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THE  CLIMATIC  FACTOK 


AS  ILLUSTEATED  IE  AEID  AMERICA 


BY 

ELLSWORTH  HUNTINGTON 

Assistant  Professor  of  Geography  at  Yale  University 


WITH  CONTRIBUTIONS  BY 


CHARLES  SCHUCHERT,  ANDREW  E.  DOUGLASS, 
AND  CHARLES  J.  KULLMER 


WASHINGTON,  D.  C. 

Published  by  the  Carnegie  Institution  of  Washington 


1914 


CARNEGIE  INSTITUTION  OF  WASHINGTON 

Publication  No.  192 


Copies  of  thi#  Bask 
were  first 

MAY  I  5  19M 


PRESS  OF 

THE  NEW  ERA  PRrNTlNO  COMPANY 
LANC.AST^.R.  PA« 


TABLE  OF  CONTENTS. 


Chapter.  Page. 

Introduction .  1-5 

Part  I.  The  Problem  of  Climatic  Changes. 

I.  The  monsoon  climate  of  Arizona  and  New  Mexico .  9 

II.  The  topographic  influence  of  aridity .  15 

III.  The  arboreal  vegetation  of  the  monsoon  desert .  21 

IV.  The  climatic  theory  of  terraces .  23 

V.  The  fluctuations  of  the  Otero  Soda  Lake .  37 

VI.  The  relation  of  alluvial  terraces  to  man .  43 

VII.  The  ancient  people  of  southern  Arizona .  47 

VIII.  Ruins  in  northern  Sonora  and  southern  New  Mexico .  65 

IX.  The  successive  stages  of  culture  in  northern  New  Mexico .  75 

X.  Southern  Mexico  as  a  test  case .  95 

XI.  A  method  of  estimating  rainfall  by  the  growth  of  trees,  by  A.  E.  Douglass .  101 

XII.  The  correction  and  comparison  of  curves  of  growth .  123 

XIII.  The  curve  of  the  big  trees .  139 

XIV.  The  interpretation  of  the  curve  of  the  Sequoia .  157 

XV.  The  peninsula  of  Yucatan .  175 

XVI.  The  shifting  of  climatic  zones  (including  the  Shift  of  the  Storm  Track,  by  Charles  J.  Kullmer) .  189 

XVII.  Guatemala  and  the  highest  native  American  civilization . 211 

XVIII.  Climatic  changes  and  Maya  history .  225 

XIX.  The  solar  hypothesis .  233 

XX.  Crustal  deformation  as  the  cause  of  climatic  changes . 255 

Part  II.  Climates  of  Geologic  Time. 

XXI.  Climates  of  Geologic  Time,  by  Charles  Schuchert .  265 

Part  III.  Tables. 

A.  Average  growth  of  451  Sequoia  trees  in  California,  by  decades  and  centuries,  beginning  with  their  youth  ; 

basis  of  corrective  factor  for  age .  301 

B.  Comparative  growth  of  short-lived  and  long-Uved  Sequoias  by  groups;  factor  for  longevity .  301 

C.  List  of  individual  Sequoia  trees  measured  in  California  in  1911  and  1912 .  302 

D.  Summary  of  Sequoia  trees,  by  groups .  307 

E.  Combined  corrective  factors  for  age  and  longevity.  Sequoia  washing toniana .  308 

F.  Growth  of  Sequoia  washingtoniana  by  groups  for  each  decade;  uncorrected  and  corrected . 311 

G.  Summary  of  growth  of  Sequoia  washingtoniana,  corrected  and  uncorrected,  including  Caspian  factor . 323 

H.  Summary  of  growth  of  trees  measured  by  the  United  States  Forest  Service .  325 

I.  Average  annual  growth  of  Sequoias . 328 

J.  Errors  of  ring  counting  in  northern  Arizona  pines . 330 

Index .  331 

iii 


LIST  OF  ILLUSTRATIONS. 


PLATES  AND  MAPS.  Facing 

page 

Plate  1 .  21 

A.  Alluvial  deposits  burying  the  bottoms  of  mesquite  trees  on  the  lower  Santa  Cruz  near  Charco  Y uua. 

B.  Typical  vegetation  of  southern  Arizona,  giant  cactus,  Cholla,  mesquite  bushes,  grease-wood,  etc. 

C.  Alluvial  terraces  and  typical  vegetation  of  a  river  valley  in  Northern  Sonora. 

Plate  2.... . 46 

A.  Ruins  of  little  stone  terraces  at  Rincon  Canyon. 

B.  DefeMive  Hohokam  walls  on  a  hilltop  near  San  Xavier. 

C.  Looking  down  from  the  top  of  the  Trincheras  of  the  Magdalena  River. 

D.  Site  of  an  ancient  village  in  Southern  Arizona;  metate  and  mani  stones  for  grinding  seeds. 

Plate  3 .  . . . .  83 

A.  Ruins  of  Tyuonyd  in  the  Canyon  de  los  Frijoles. 

B.  Ruins  of  Pueblo  Bonita  in  Chaco  Canyon. 

Plate  4 .  104 

The  cross  identification  of  rings  of  growth. 

Plate  5 .  139 

A.  The  Boule  tree,  a  Sequoia  probably  2,500  years  old. 

B.  Young  and  middle-aged  Sequoia  in  a  valley  bottom. 

Plate  6 .  145 

The  dying  out  of  rings  in  a  young  Sequoia  at  Dillonwood. 

Plate? .  146 

The  effect  of  injuries  upon  a  young  Sequoia. 

Plates .  183 

A.  A  market-place  in  Yucatan,  showing  the  best  modern  architecture. 

B.  A  typical  house  in  Yucatan. 

C.  Archway  at  Labna. 

D.  Farmer’s  hut  in  the  midst  of  Labna. 

E.  Ruins  of  Chac-multun. 

Plate  9 .  189 

A.  Carved  head  at  Baul  in  the  Pacific  coffee  belt  of  Guatemala. 

B.  A  bit  of  a  temple  wall  at  Copan. 

C.  One  of  the  Stelae  at  Copan. 

D.  Forest  in  which  ruins  at  Kichen-kanab  are  located. 

Plate  10 . 211 

A.  The  church  of  Esquipulas,  representing  the  best  Spanish  architecture  in  Guatemala. 

B.  The  riverward  side  of  the  main  citadel  at  Copan. 

Plate  11 . 218 

A.  The  ruins  of  Quiche,  the  most  extensive  on  the  Guatemalan  plateau. 

B.  Near  view  of  the  most  imposing  ruins  of  Quiche. 

Plate  12 . 230 

A.  Stelse  inscribed  with  hieroglyphics  at  Quirigua. 

B.  The  ruins  of  Copan. 


Sketch  map  of  Arizona  and  New  Mexico,  showing  location  of  places  mentioned  in  the  text. 

Map  2 .  175 

Sketch  map  of  a  part  of  Central  America,  showing  location  of  Maya  ruins. 

TEXT  CUTS. 

Page. 

1.  Rainfall  of  Arizona  and  New  Mexico .  10 

2.  Annual  rainfall  at  Tucson,  Arizona,  1868-1912 . 11 

3.  Winter  and  summer  rainfall  at  Tucson .  13 

4.  Comparison  of  3-year  means  of  winter  and  summer  rainfall  at  Tucson .  13 

5.  Cross-section  illustrating  the  formation  of  climatic  terraces .  27 

6.  Profile  of  climatic  terraces .  33 

7.  Rainfall  and  emigration  in  Europe .  89 

8.  Cross-section  of  alluvial  terraces  in  mountain  valleys  near  the  City  of  Mexico .  100 

9.  Annual  growth  of  trees  at  Prescott .  107 

10.  Annual  rainfall  and  growth  of  trees  (Group  V)  at  Prescott .  108 

11.  Annual  growth  of  trees  at  Flagstaff,  and  variations  in  annual  rainfall  according  to  month  which  is  reckoned 

as  the  beginning  of  the  year . .  109 

12.  Growth  of  individual  trees  compared  with  precipitation  at  Flagstaff .  Ill 

13.  14.  Effect  of  monthly  distribution  of  precipitation  on  thickness  of  rings  of  growth .  Ill 

15.  Monthly  and  yearly  precipitation  from  1866  to  1909,  and  size  and  character  of  rings .  112 


IV 


LIST  OF  ILLUSTRATIONS. 


V 

16.  Actual  tree  growth  compared  with  growth  calculated  from  rainfall .  113 

17.  Five-year  smoothed  curves  of  rainfall  and  tree  growth  at  Prescott .  113 

18.  Actual  rainfall  compared  with  rainfall  calculated  from  gi’owth  of  trees,  Arizona .  114 

19.  Annual  growth  of  trees  at  Flagstaff  since  1385  A.D .  116 

20.  500-year  curve  of  tree  ^owth,  20-year  means .  117 

21.  A  possible  150-year  period .  117 

22.  Mean  curve  of  the  21-year  cycle .  117 

23.  Variations  of  the  11-year  cycle .  118 

24.  Comparison  of  eleven  4-year  cycles  in  tree  growth,  rainfall,  temperature,  and  inverted  sun-spot  numbers. . .  119 

25.  Sun-spots  and  the  growth  of  trees  at  Eberswalde,  Germany .  120 

26.  Ideal  curves  illustrating  correction  for  age .  125 

27.  Ideal  curve  illustrating  correction  for  longevity .  127 

28.  Curve  of  growth  and  correction  for  age  of  yellow  pine  in  New  Mexico .  128 

29.  Curve  of  growth  of  50  yellow  pines  over  280  years  of  age .  129 

30.  Variation  in  radial  growth  by  decades .  131 

31.  Curves  of  growth  of  American  trees .  133 

32.  Curves  of  growth  of  western  yellow  pine  in  New  Mexico  and  Idaho .  135 

33.  Rainfall  of  Idaho  compared  with  that  of  New  Mexico .  136 

34.  Ideal  diagram  to  illustrate  the  dropping  of  rings .  148 

35.  Sequoia  washingtoniana,  corrective  factor  for  age  during  first  250  years  of  hfe .  150 

36.  Sequoia  washingtoniana,  corrective  factor  for  age,  plotted  by  centuries .  151 

37.  Sequoia  washingtoniana,  corrective  factor  for  longevity .  152 

38.  Curve  of  growth  of  the  Sequoia  washingtoniana  in  California .  153 

39.  Effect  of  flaring  buttresses  on  the  measurement  of  rings  of  growth .  154 

40.  Annual  rainfall  at  selected  stations  in  California .  158 

41.  Monthly  distribution  of  precipitation  in  California .  160 

42.  Rainfall  at  Portersville  compared  with  growth  of  Sequoias  at  Dillonwood .  161 

43.  Annual  growth  of  111  Sequoias  at  Hume .  162 

44.  Growth  of  trees  at  Hume,  and  rainfall  at  Fresno .  163 

45.  Mean  monthly  distribution  of  rainfall  compared  with  distribution  in  exceptional  years .  164 

46.  Conservation  factor  in  the  relation  of  growth  and  rainfall,  method  1 .  166 

47.  Conservation  factor  in  the  relation  of  growth  and  rainfall,  method  II .  166 

48.  Tree  growth  in  California  calculated  from  rainfall .  167 

49.  Rainfall  by  months  in  favorable  and  unfavorable  years .  170 

50.  Changes  of  climate  in  California  and  western  Asia  dvuing  historic  times .  172 

51.  Storm  frequency,  1878-1887 .  191 

52.  Storm  frequency,  January .  194 

53.  Storm  frequency,  February .  194 

54.  Storm  frequency,  March .  195 

55.  Storm  frequency,  April . ' .  195 

56.  Storm  frequency.  May .  196 

57.  Storm  frequency,  June .  196 

58.  Storm  frequency,  July .  197 

59.  Storm  frequency,  August .  197 

60.  Storm  frequency,  September .  198 

61.  Storm  frequency,  October .  198 

62.  Storm  frequency,  November .  199 

63.  Storm  frequency,  December . 7 .  199 

64.  Storm  frequency.  Year  maps  for  1878-1887,  after  Dunwoody,  and  1899-1908,  after  Kullmer,  showing  shift 

of  storm  track .  201 

65.  Changes  in  storm  frequency  by  months  according  to  longitude . 202 

66.  Changes  in  storm  frequency  by  months  irrespective  of  longitude  and  latitude .  202 

67.  Changes  in  storm  frequency  by  months  according  to  longitude  in  latitude  50“-55° .  202 

68.  Changes  in  storm  frequency  by  months  according  to  longitude  in  latitude  45°-50° .  203 

69.  Changes  in  storm  frequency  by  months  according  to  longitude  in  latitude  30°-35° . 204 

70.  Changes  in  storm  frequency  by  months  according  to  longitude  in  latitude  25'’-30° . 204 

71.  Summary  of  differences  in  storm  frequency,  1878-1887  and  1899-1908 .  204 

72.  Changes  of  climate  in  California  for  2,000  years . 209,  231 

73.  Diagrammatic  sections  of  wall  and  deposits  at  Copan  Ruins .  214 

74.  Relation  of  terraces  and  ruins  at  Copan . 214 

75.  The  Relation  of  sun-spots  and  tree  growth  in  the  11-year  cycle .  239 

76.  The  sun-spot  cycle  and  terrestrial  phenomena .  240 

77.  The  com  crop  of  the  United  States,  1901,  a  “lean”  year .  244 

78.  The  com  crop  of  the  United  States,  1906,  a  “fat”  year .  244 

79.  The  corn  crop  of  the  United  States,  1908 .  245 

80.  The  com  crop  of  the  United  States,  1909 . 245 

81.  Variations  of  the  solar  constant  and  monthly  departures  from  mean  temperature  at  Arequipa . 246 

82.  Monthly  departures  of  temperature  in  South  Equatorial  regions,  showing  agreement . 247 

83.  Monthly  departures  of  temperature  in  North  and  South  Equatorial  regions,  showing  disagreement . 248 

84.  Monthly  departures  of  temperature  in  North  America  compared  with  Arequipa  in  Peru .  249 

85.  The  Relation  of  volcanoes,  sun-spots,  and  terrestrial  temperature .  252 

86.  Geological  changes  of  climate  and  movements  of  the  Earth’s  crust . 256 

87.  Map  of  Pleistocene  glaciation .  266 

88.  Paleogeography  and  glaciation  of  early  Permic  times .  267 

89.  Map  of  Proterozoic  glaciation .  270 

90.  Chart  of  geological  climates.  Paleometeorology .  285 


NOTE  TO  THE  READER. 

This  volume  as  a  whole  deals  with  climate,  but  various  parts  are  concerned  with 
particular  aspects  of  the  problem.  The  reader  who  is  interested  in  one  special  phase  is 
referred  to  the  following  chapters: 

Physical  aspects  of  the  Southwest,  Chapters  I  to  VI. 

The  Ancient  People  of  the  Southwest,  Chapters  VII  to  X. 

The  Measurement  of  Rainfall  by  the  Growth  of  Trees,  Chapters  XI  to  XIV. 

The  Maya  Civilization  and  Changes  of  Climate  in  the  Torrid  Zone,  Chapters  XV  to  XVIII. 

Theories  of  Climatic  Changes,  Chapters  XIX  and  XX. 

The  Climate  of  the  Geological  Past,  Chapter  XXI. 

The  volume  may  be  divided  in  another  way  according  to  the  sciences  with  which  the 
different  chapters  are  more  especially  concerned.  In  this  division,  however,  it  must  be 
recognized  that  there  is  much  overlapping,  for  the  same  chapter  often  deals  with  several 
sciences. 

Climatology,  Chapters  I,  XIV,  XVI,  XIX. 

Geology,  Chapters  II,  IV,  V,  VI,  X,  XX,  XXL 

Botany,  Chapters  III,  XI,  XII,  XIII,  XIV. 

Archeology,  Chapters  VI,  VII,  VIII,  IX,  X,  XVI,  XVII,  XVIII. 

Ethnology,  Chapters  VII,  XV,  XVII,  XVIII. 

The  reader  who  desires  to  understand  the  main  outline  of  the  theories  here  presented, 
but  does  not  care  to  go  through  all  the  details  of  evidence  is  advised  to  read  the  Introduc¬ 
tion,  and  Chapters  VI,  VII,  IX,  XIII,  XIV,  XVI,  XVII,  XIX,  and  XX. 


VI 


THE  CLIMATIC  FACTOR 
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INTRODUCTION. 


Climate  as  an  element  of  physical  environment  is  so  well  recognized  that  there  is  no 
need  to  demonstrate  its  importance.  By  common  consent  it  is  held  to  be  a  primary 
factor  not  only  in  the  life  of  plants,  animals,  and  man  as  they  exist  to-day,  but  in  their 
entire  evolution.  Moreover,  among  the  main  elements  of  physical  environment  it  alone  is 
subject  to  pronounced  changes  in  comparatively  brief  periods.  The  form  of  the  lands, 
the  location  of  mountains,  and  the  composition  of  the  atmosphere  are  doubtless  all  subject 
to  great  changes,  but  these  are  too  slow  to  have  much  effect  upon  a  single  generation  of 
living  beings  or  even  upon  all  the  generations  that  have  existed  during  the  period  since 
man  emerged  from  barbarism.  Small  climatic  changes,  however,  such  as  those  from  one 
year  to  the  next,  or  from  one  decade  to  another,  are  constantly  in  progress,  and  their  far- 
reaching  results  are  a  matter  of  every-day  experience.  Moreover,  it  is  quite  possible  that 
larger  changes  have  taken  place  during  the  past  2,000  or  3,000  years,  and  if  this  is  the 
case  their  effects  must  have  been  correspondingly  important.  The  investigation  of  this 
possibility  is  the  purpose  of  this  volume. 

The  study  of  changes  of  climate  naturall}’'  divides  itself  into  two  parts,  relating  to  the 
present  and  to  the  past.  The  facts  as  to  the  present  are  being  rapidly  gathered  by  the 
excellent  work  of  the  various  National  Weather  Bureaus  of  the  world.  The  facts  as  to 
the  remote  past  are  being  studied  minutely  by  geologists  so  far  as  they  relate  to  geological 
times.  Comparatively  little,  however,  is  known  as  to  the  state  of  affairs  during  the  period 
covered  by  history  and  man’s  later  development.  Yet  a  knowledge  of  this  period  is 
essential.  In  the  first  place,  it  is  only  by  accurate  knowledge  of  past  variations  that  we 
may  hope  to  ascertain  the  causes  of  present  variations,  and  thus  to  predict  those  which 
will  occur  in  the  future.  Geological  evidence  of  course  tells  us  much  about  the  past,  but 
it  pertains  largely  to  periods  too  remote  to  be  of  great  present  importance,  and  its  phe¬ 
nomena  can  not  be  dated  with  accuracy  in  terms  of  years.  Hence  something  else  is  needed 
to  fill  the  gap  between  such  geological  phenomena  as  the  glacial  period  and  our  modern 
climatic  records  covering  scarcely  a  century.  In  the  second  place,  a  mathematical  investi¬ 
gation  of  the  chief  effects  of  present  climatic  conditions  may  do  much  to  show  how  far 
human  habits,  customs,  physiological  traits,  and  mental  character  are  influenced  by 
physical  environment,  but  it  is  impossible  to  determine  the  exact  effect  of  present  con¬ 
ditions  until  we  know  how  long  those  conditions  have  lasted  and  how  the  environment  of 
the  past,  especially  during  the  last  2,000  or  3,000  years,  differed  from  that  of  the  present. 
Hence  along  many  lines  the  study  of  the  climatic  variations  of  historic  times  is  essential 
as  the  foundation  of  future  work. 

The  present  volume  is  an  attempt  to  determine  the  sequence  and  character  of  such 
variations  on  the  basis  of  evidence  in  the  drier  portions  of  America  from  Guatemala  on  the 
south  to  Idaho  on  the  north.  A  large  number  of  phenomena  from  the  diverse  fields  of 
geology,  archeology,  history,  and  botany  seem  to  agree  in  indicating  that  during  the  past 
3,000  years  North  America  has  been  subject  to  pronounced  climatic  pulsations  similar 
to  those  which  appear  to  have  taken  place  in  Asia  and  other  parts  of  the  Old  World.  In 
the  temperate  portions  of  the  Eastern  Hemisphere  the  climate  of  the  past  appears  on  the 
whole  to  have  been  distinctly  moister  than  that  of  the  present.  The  change  from  the 
past  to  the  present,  however,  does  not  seem  to  have  been  gradual  and  regular,  but  pulsatory 
or  cyclic,  so  that  certain  periods  have  been  exceptionally  dry,  while  others  have  been  wet. 
In  America  the  same  appears  to  be  true. 

2 


1 


2 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


The  facts  set  forth  in  this  volume  are  the  result  of  investigations  carried  on  in  coopera¬ 
tion  with  the  Department  of  Botanical  Research  of  the  Carnegie  Institution  of  Washington, 
at  the  invitation  of  the  Director,  Doctor  D.  T.  MacDougal.  The  first  field  season,  March, 
April,  and  May,  1910,  was  devoted  to  the  study  of  a  relatively  restricted  area  centering 
at  Tucson,  the  site  of  the  Desert  Botanical  Laboratory  in  southern  Arizona,  and  extending 
southwestward  for  150  miles  to  the  shores  of  the  Gulf  of  CaUfornia  in  northwestern  Mexico. 
During  the  second  season  the  months  of  March  and  April,  1911,  were  devoted  to  the 
investigation  of  selected  sites  in  various  parts  of  New  Mexico,  while  May  and  June  were 
occupied  with  measurements  of  the  rate  of  growth  of  about  200  Sequoia  trees  in  the  central 
parts  of  the  Sierra  Nevada  Mountains  in  Cahfornia.  The  third  season  was  divided  into 
two  portions.  In  the  first  place,  six  weeks  during  March  and  April,  1912,  were  spent  among 
the  lakes  and  ancient  ruins  of  southern  Mexico  and  Yucatan.  In  the  second  place,  the 
work  upon  the  Sequoias  in  California  was  carried  further,  and  about  250  more  trees  were 
measured.  Finally,  in  March  and  April,  1913,  independently  of  the  Carnegie  Institution, 
the  author  made  a  journey  to  Guatemala  for  the  purpose  of  investigating  the  ruins  of 
that  region  and  their  relation  to  the  physical  surroundings  and  vegetation  of  the  country. 

Throughout  the  work  much  attention  was  given  to  the  influence  of  the  present  climatic 
conditions  upon  physiography  and  upon  the  habits  and  distribution  of  plants  and  animals, 
including  man.  No  attempt  will  be  made  to  deal  with  these  subjects  here,  however,  except 
in  so  far  as  they  bear  upon  changes  of  chmate.  The  purpose  of  this  volume  is  primarily 
to  investigate  the  extent  and  nature  of  such  changes  and  our  attention  will  be  devoted 
almost  exclusively  to  that  subject,  while  the  interesting  problems  of  the  relation  of  climate 
to  human  character  and  history  will  be  left  for  another  volume.  The  first  portion  of  our 
investigations  will  be  concerned  entirely  with  New  Mexico,  Arizona,  and  the  adjacent 
parts  of  the  Mexican  state  of  Sonora.  Inasmuch  as  an  intelligent  knowledge  of  present 
climatic  conditions  is  essential  to  a  full  understanding  of  the  past,  the  present  chmate  of 
those  regions  and  its  relation  to  the  great  climatic  zones  of  the  earth  as  a  whole  wiU  form 
our  first  subject  of  consideration.  A  minute  knowledge  of  the  land  forms  of  the  region 
is  not  necessary  for  our  present  purpose,  but  a  clear  conception  of  the  main  types  and 
of  their  relation  to  climatic  conditions  is  advisable.  Accordingly  a  chapter  will  be  devoted 
to  the  general  aspect  of  New  Mexico,  Arizona,  and  Sonora,  and  to  the  chief  types  of  physio¬ 
graphic  forms  commonly  found  there.  To  complete  the  picture  a  brief  chapter  on  vegeta¬ 
tion  will  be  added,  not  from  the  point  of  view  of  the  botanist  but  of  the  geographer. 

Having  gained  a  general  idea  of  the  physical  aspects  of  New  Mexico  and  Arizona,  we 
shall  be  prepared  to  turn  to  some  of  the  details  which  furnish  evidence  as  to  past  climatic 
conditions.  First  we  shall  take  up  those  fines  of  inquiry  which  involve  only  physical 
processes  without  respect  to  man.  Among  these  a  foremost  place  is  occupied  by  the 
alluvial  terraces  which  are  so  widely  distributed  throughout  all  arid  mountainous  regions. 
Their  importance  as  possible  indicators  of  climatic  changes  is  so  great  that  I  shall  consider 
the  problem  of  their  formation  in  detail.  The  strands  of  ancient  lakes  are  often  closely 
associated  with  river  terraces,  and  the  conclusions  to  be  drawn  from  them  are  similar. 
Our  region  has  so  few  lakes  and  these  few  have  been  so  little  investigated  that  they  are  of 
less  importance  than  many  other  fines  of  evidence.  Nevertheless,  the  Otero  soda  lake 
near  Alamogordo  in  New  Mexico  and  the  group  of  small  lakes  near  the  City  of  Mexico  are 
of  such  interest  as  to  warrant  a  somewhat  full  discussion.  The  desiccated  bed  of  the  Otero 
Lake  presents  evidences  of  a  changing  climate  not  only  in  its  old  strands,  but  in  the  re¬ 
markable  series  of  gypsum  dunes  of  various  ages  which  surround  it;  while  in  the  Mexican 
lakes  natural  causes  appear  to  have  induced  variations  in  size  even  during  the  period  since 
the  coming  of  the  Spaniards. 

From  the  purely  physiographic  portion  of  our  investigations  in  Arizona,  New  Mexico, 
and  old  Mexico,  we  shall  proceed  to  the  main  phase  of  the  subject — the  study  of  traces  of 


INTRODUCTION. 


3 


ancient  human  occupation.  In  this  part  of  the  work  we  shall  examine  a  large  number  of 
ruins  scattered  from  the  shore  of  the  Gulf  of  Cahfornia  to  the  northern  limits  of  New 
Mexico,  500  miles  away.  Except  among  a  few  archeologists,  the  number  of  ruins  is  rarely 
appreciated.  The  ruins  not  only  indicate  a  considerable  degree  of  culture,  but  they  show 
distinctly  that  different  races  occupied  the  same  sites  in  succession.  The  successive  occu¬ 
pations  were  separated  by  periods  of  abandonment,  due  possibly  to  climatic  causes,  or 
perhaps  to  something  quite  different,  but  at  least  well  worthy  of  study.  In  considering 
the  ancient  ruins  and  their  prehistoric  inhabitants  it  is  essential  to  keep  fairly  in  mind  two 
opposing  theories.  The  first,  which  is  usually  accepted,  holds  that  the  large  number  of 
ruins  does  not  indicate  a  correspondingly  large  population,  and  that  the  physical  conditions 
of  the  country  in  the  past,  just  as  at  present,  forbade  any  great  number  of  inhabitants. 
The  other,  which  is  accepted  by  only  a  few  scholars,  holds  that  the  ruins  were  occupied  by 
a  relatively  dense  population  which  persisted  for  a  long  time.  This  could  have  been 
possible  only  on  the  assumption  of  greater  rainfall  than  now,  and  therefore  those  who 
hold  this  view  believe  in  changes  of  climate. 

The  lines  of  reasoning  followed  thus  far  are  similar  to  those  which  I  have  employed  in 
respect  to  various  countries  of  Asia,  and  which  were  first  set  forth  in  a  volume  entitled 
“Exploration  in  Turkestan,”  published  by  the  Carnegie  Institution  of  Washington  in  1905, 
and  have  been  amplified  and  revised  in  “The  Pulse  of  Asia”  and  “Palestine  and  its  Trans¬ 
formation,”  published  in  1907  and  1911,  respectively.  The  conclusions  derived  from  these 
lines  of  reasoning  are  open  to  the  criticism  that  a  preconceived  theory  may  have  led  to 
the  interpretation  of  phenomena  according  to  that  theory.  Hence,  before  the  conclusions 
here  indicated  deserve  final  acceptance,  it  is  necessary  to  compare  them  with  the  results 
obtained  by  the  observations  of  other  unprejudiced  workers,  or  with  the  independent 
results  of  some  new  method  in  which  the  personal  equation  plays  no  part.  Fortunately 
the  work  of  Professor  A.  E.  Douglass,  of  the  University  of  Arizona,  suggests  a  method  by 
which  old  trees  may  be  used  as  a  mathematical  measuring-rod  in  order  to  determine 
exactly  what  climatic  events  have  occurred  during  the  last  2,000  or  3,000  years.  Accord¬ 
ingly,  considerable  space  will  be  devoted  to  setting  forth  the  results  of  the  measurement 
of  the  rate  of  growth  of  nearly  500  Sequoia  trees  among  the  Sierra  Mountains  in  California. 
A  large  number  of  other  measurements  of  trees  by  the  United  States  Forest  Service  have 
been  kindly  put  at  the  disposal  of  the  Carnegie  Institution  of  Washington  by  the  Forester, 
Mr.  Henry  S.  Graves,  and  a  discussion  of  them  is  included  in  this  volume.  By  purely 
mathematical  methods,  unaffected  by  any  personal  bias,  it  has  been  possible  to  obtain 
curves  indicating  the  climatic  pulsations  of  the  last  3,000  years.  A  comparison  of  these 
curves  with  the  results  obtained  from  other  lines  of  evidence,  both  in  America  and  Asia, 
shows  that  in  spite  of  certain  disagreements  the  general  climatic  history  of  both  continents 
appears  to  have  been  characterized  by  similar  pulsations  having  a  periodicity  of  hundreds 
or  thousands  of  years. 

If  the  conclusions  outlined  above  are  accepted,  they  may  perhaps  furnish  a  key  to  the 
pre-Columbian  chronology  of  America.  Apparently  the  Southwest  has  been  first  relatively 
inhabitable  and  then  relatively  uninhabitable  during  periods  lasting  hundreds  of  years. 
The  dates  of  these  periods  are  ascertainable  from  ancient  trees.  Each  propitious  period 
has  probably  been  a  time  of  expanding  cultme  and  comparatively  dense  population,  while 
the  unpropitious  periods  have  been  times  of  invasion,  disaster,  and  depopulation.  Archeo¬ 
logical  study  has  begun  to  differentiate  periods  of  this  sort,  but  has  been  unable  to  date  or 
correlate  them.  If  the  evidence  of  climate  be  considered  together  with  that  of  archeology, 
we  may  perhaps  at  length  be  able  to  overcome  the  absence  of  written  documents  so  far  as 
to  construct  a  fairly  intelligible  record  of  the  history  of  our  ancient  predecessors. 

The  broader  the  area  under  observation,  the  greater  is  the  probability  of  accurate 
results.  Hence,  after  two  field  seasons  in  Arizona,  New  Mexico,  and  Sonora,  it  seemed  wise 


4 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


to  extend  the  work  more  than  1,300  miles  southward  to  southern  Mexico  and  Yucatan, 
and  finally  400  miles  farther  into  Guatemala  and  Honduras.  Here  again  the  lines  of 
reasoning  previously  employed  in  Asia  and  later  in  the  United  States  and  northern  Mexico 
gave  similar  results.  In  Yucatan  and  Guatemala,  however,  a  new  type  of  phenomena 
was  also  found,  which  confirmed  the  previous  conclusions  most  interestingly.  In  that 
tropical  region  the  presence  of  magnificent  ruins  in  the  midst  of  dense  forests  seems  to 
indicate  changes  of  climate  contrary  to  those  of  the  regions  farther  north.  On  the  whole 
the  country  appears  to  be  moister  than  it  was  several  thousand  years  ago,  instead  of  drier, 
as  in  regions  farther  north.  This  at  first  sight  appears  contradictory,  but  in  reality  it 
confirms  a  conclusion  derived  from  other  evidence,  namely,  that  changes  of  climate  are 
probably  characterized  by  the  shifting  of  the  world’s  great  climatic  zones  from  north  to 
south,  and  the  reverse. 

Having  reached  this  conclusion,  we  find  ourselves  able  to  test  it  by  means  of  another 
of  wholly  independent  nature  based  on  a  comparison  of  historic  events  and  climatic  changes 
in  Europe  and  Asia.  This  second  conclusion  is  that  while  the  course  of  history  depends 
upon  a  vast  number  of  factors  and  its  details  are  due  to  what  may  be  designated  as  purely 
human  causes,  yet  in  its  broader  outlines  it  is  profoundly  affected  by  climatic  changes. 
These  may  alter  economic  conditions,  they  may  disturb  the  adaptation  of  a  race  to  its 
environment  by  fostering  special  diseases,  or  they  may  force  people  to  move  out  of  a 
habitat  where  they  can  no  longer  compete  with  nature.  In  Yucatan  and  the  neighboring 
parts  of  Central  America  the  dense  tropical  forests  and  their  deadly  malarial  fevers  are 
man’s  chief  enemy.  Our  study  of  the  terraces,  ruins,  trees,  and  other  phenomena  of  the 
United  States  and  northern  Mexico  leads  to  the  hypothesis  that  the  forests  of  Yucatan 
and  the  surrounding  regions  have  alternately  increased  and  diminished  in  size,  the  increase 
coming  at  times  when  aridity  prevailed  in  regions  such  as  CaUfornia,  and  the  decrease  during 
California’s  moist  times.  Our  hypothesis  as  to  the  relation  of  changes  of  climate  and 
history  leads  to  the  inference  that  civilization  in  Central  America  would  thrive  when  the 
forests  diminished  and  would  decline  when  they  increased.  A  comparison  of  the  chmatic 
periods  indicated  by  the  Sequoias  with  the  events  of  the  history  of  the  ancient  Mayas  of 
Yucatan,  as  recorded  on  monuments  and  in  chronicles,  shows  that  our  expectations  are 
realized  to  a  considerable  degree.  Thus  both  conclusions  are  strengthened. 

The  degree  of  certainty  given  to  our  conclusions  by  the  agreement  of  the  evidence  of 
old  trees  with  that  derived  from  other  sources  brings  us  to  the  point  where  we  may  reason¬ 
ably  attempt  to  ascertain  the  cause  of  changes  of  climate.  In  such  an  attempt  the  first 
matter  to  claim  attention  is  a  certain  degree  of  coincidence  between  the  phenomena  of 
climate  and  those  of  the  sun.  There  are  many  reasons  for  thinking  that  the  well-known 
sun-spot  cycle  of  11  years  is  related  to  a  distinct  climatic  cycle.  The  longer,  but  less 
thoroughly  estabUshed  35-year  cycle  of  Bruckner  also  appears  to  be  correlated  with  the 
activity  of  the  sun.  These  things,  as  has  often  been  pointed  out,  suggest  that  our  minor 
climatic  fluctuations  maybe  due  to  slight  variations  in  the  intensity  of  the  sun’s  radiation. 
The  work  of  Langley,  Abbott,  and  others  proves  that  the  sun’s  radiation  actually  does 
vary,  while  that  of  Koppen,  Newcomb,  and  many  more  proves  that  the  temperature  of 
the  earth’s  atmosphere  shows  a  corresponding  variation.  The  terrestrial  variation  is  so 
slight,  however,  and  is  so  irregular  outside  of  equatorial  regions,  that  some  of  the  best 
authorities  doubt  whether  it  is  sufficient  to  produce  appreciable  results.  Opposed  to  this 
is  the  fact  that  by  almost  universal  consent  students  of  glaciation  beheve  that  a  permanent 
lowering  of  the  earth’s  mean  temperature  to  the  extent  of  from  3°  to  10°  C.  would  produce 
a  glacial  period.  The  most  conservative  estimates  of  the  change  in  terrestrial  temperature 
between  the  minimum  and  maximum  of  sun-spots  is  about  0.5°  C.  This  is  so  large  a  frac¬ 
tion  of  the  change  needed  to  produce  glaciation  that  it  seems  as  if  it  must  produce  some 
appreciable  meteorological  results. 


INTRODUCTION. 


It  is  true  that  attempts  to  detect  such  results  have  hitherto  proved  contradictory,  but 
this  is  not  surprising.  It  seems  to  be  due  partly  to  the  lack  of  long,  homogeneous  records 
and  partly  to  failure  to  make  due  allowance  for  the  different  degrees  to  which  different  kinds 
of  phenomena,  such  as  temperature,  pressure,  wind,  and  rain,  must  lag  behind  their  cause, 
especially  under  conditions  such  as  those  of  the  atmosphere,  where  large  quantities  of  heat 
are  transferred  from  one  region  to  another.  The  new  method  of  investigation  of  climate 
by  means  of  the  growth  of  trees,  as  elaborated  by  Professor  Douglass  in  his  contribution 
to  this  volume,  furnishes  long,  homogeneous  records,  and  these  show  a  distinct  sun-spot 
cycle.  The  careful  researches  of  Arctowski  upon  '‘pleions”  and  “anti-pleions’’  seem  not 
only  to  demonstrate  a  relation  between  solar  phenomena  and  terrestrial  climate,  but  also 
to  show  why  the  manifestation  of  this  relationship  is  irregular  and,  at  first  sight,  con¬ 
tradictory.  These  things  lead  to  the  conclusion  that  the  small  climatic  cycles  now  in 
progress  upon  the  earth  are  in  large  measure  due  to  variations  in  the  sun. 

In  regard  to  greater  climatic  changes,  it  appears  that  the  pulsations  of  the  past  3,000 
years  are  too  large  to  be  due  to  fortuitous  rearrangements  of  the  earth’s  atmosphere  because 
of  purely  terrestrial  causes.  On  the  other  hand,  they  occur  too  rapidly  to  be  due  to  pre¬ 
cession  of  the  equinoxes,  changes  in  the  carbonic-acid  content  of  the  air,  or  deformation 
of  the  earth’s  crust.  Hence  we  are  led  to  conclude  that  they,  too,  are  due  to  variations 
in  the  sun.  The  same  conclusion  seems  to  apply  to  glacial  and  interglacial  epochs,  since 
their  characteristics  appear  to  be  identical  in  nature  with  those  of  the  pulsations  of  historic 
times,  although  differing  greatly  in  degree.  In  explanation  of  still  greater  changes,  how¬ 
ever,  such  as  the  radical  difference  between  the  distribution  of  climatic  zones  in  the  Permian 
and  Pleistocene  eras,  something  else  is  demanded.  In  Part  II  of  this  volume  the  matter 
is  fully  presented  by  Professor  Schuchert  from  the  standpoint  of  the  paleontological  geolo¬ 
gist.  We  are  there  led  to  the  conclusion  that  while  changes  in  the  amount  of  carbonic-acid 
gas  in  the  atmosphere  may  explain  certain  climatic  phenomena,  they  can  not  explain  this 
particular  feature.  Crustal  deformation,  on  the  contrary,  seems  fully  adequate  to  cause 
just  such  a  redistribution  of  zones  as  we  find  from  time  to  time  in  geologic  history.  It 
apparently  can  not,  however,  account  for  the  climatic  instability  which  often  accompanies 
or  immediately  follows  periods  of  crustal  deformation,  that  is,  for  fluctuations  from  glacial 
to  interglacial  conditions  and  for  minor  pulsations.  In  explanation  of  these  it  seems 
reasonable  to  turn  back  to  our  solar  h3rpothesis.  Thus  we  are  led  to  the  final  hypothesis 
that  for  some  unknown  cause  both  the  earth  and  the  sun  have  been  repeatedly  thrown  into 
activity  at  approximately  the  same  time.  The  activity  of  the  earth  seems  to  manifest  itself 
in  the  changes  of  form  whereby  continents  are  uplifted  and  mountain  ranges  shoved  up. 
That  of  the  sun  seemingly  displays  itself  in  pulsations  which  give  rise  to  climatic  variations 
of  every  grade,  beginning  with  glacial  and  interglacial  epochs  and  ending  with  little  cycles 
like  that  of  the  sun-spots. 

Here  we  leave  the  matter,  but  not  without  a  word  of  caution.  Throughout  this  volume 
our  purpose  is  not  to  develop  the  hypothesis  just  outlined  as  to  the  interrelation  of  solar 
activity,  crustal  deformation,  and  climatic  changes.  That  hypothesis,  important  as  it 
may  prove,  is  by  its  very  nature  open  to  grave  question.  At  best  it  is  merely  a  corol¬ 
lary  of  our  main  conclusion,  whose  truth  or  falsity  is  in  no  way  dependent  upon  it.  The 
primary  purpose  of  this  book  is  to  investigate  any  possible  climatic  changes  which  may 
have  taken  place  in  historic  times.  Our  main  conclusion  is  that  such  changes  have  taken 
place  and  that  they  have  been  of  a  pulsatory  nature.  All  other  questions  are  here  sub¬ 
ordinate,  and  the  truth  or  falsity  of  this  conclusion  is  the  point  upon  which  attention 
should  be  focused. 


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PART  I. 

THE  PROBLEM  OF  RECENT  CLIMATIC  CHANGES. 


7 


-•  _  ■ 


CHAPTER  I. 

THE  MONSOON  CLIMATE  OF  ARIZONA  AND  NEW  MEXICO. 


The  climate  of  Arizona,  New  Mexico,  and  northern  Sonora  is  of  a  peculiar,  transitional 
type.  It  may  be  defined  as  a  subtropical  continental  climate  of  the  monsoon  variety. 
It  resembles  that  of  the  provinces  of  the  Punjab,  Rajputana,  and  Sind  in  northern  India 
more  closely  than  that  of  any  other  part  of  the  world.  As  the  region  extends  from  about 
north  latitude  28°  in  Mexico  to  37°  in  northern  New  Mexico  and  Arizona,  its  subtropical 
position  brings  most  of  it  within  the  great  world-zone  where  high  pressure  and  consequent 
aridity  normally  prevail.  Here  the  main  movement  of  the  air  is  downward  and  outward; 
and  here  the  northeasterly  winds  of  the  trade-wind  zone  and  the  southw^esterly  winds  of 
the  zone  of  prevailing  westerlies  find  their  origin. 

If  the  climatic  zones  of  the  earth  were  not  interfered  with  by  the  different  rates  at 
which  land  and  sea  are  heated  and  cooled,  seasonal  changes  would  bring  this  region  within 
the  range  of  the  prevailing  westerlies  and  their  rain-bringing  cyclonic  storms  in  winter, 
and  within  the  trade-wind  belt  in  summer.  In  winter  the  country  would  receive  a  fair 
amount  of  rain  for  a  few  months,  the  edges,  so  to  speak,  of  the  great  storms  which  whirl 
across  more  northerly  regions  not  only  in  winter  but  in  summer.  During  the  rest  of  the 
year  it  would  be  rainless,  for  in  spring  and  fall  it  would  be  in  the  subtropical  zone  of  high 
pressure  and  descending  air,  while  in  summer  the  trades  would  blow  across  it  from  the 
northeast.  Inasmuch  as  the  trades  would  come  from  a  dry  interior,  they  would  bring  no 
rain.  As  a  matter  of  fact,  however,  the  trade-winds  are  never  well  developed  in  Aiizona 
and  New  Mexico,  and  herein  lies  the  explanation  of  the  most  peculiar  characteristics  of  the 
climate.  The  cyclonic  storms  of  the  westerlies  in  winter  and  the  descending  air  of  the 
subtropical  ‘‘horse  latitudes”  in  spring  and  autumn  give  rise  respectively  to  the  rain  and 
the  aridity  which  would  be  expected.  In  summer,  however,  because  of  the  great  size  of 
the  continent  of  North  America,  the  trade  winds  which  would  be  expected  do  not  appear; 
their  place  is  taken  by  relatively  moist  winds  which  blow  in  general  from  the  south,  and 
may  be  called  monsoons  for  lack  of  any  more  appropriate  name. 

In  order  to  give  definiteness  to  our  discussion  of  the  climate  of  the  southwest,  let  us 
recall  the  familiar  general  principles  of  the  effect  of  continents  upon  temperature,  pressure, 
winds,  and  rainfall.  Land  masses,  as  is  well  known,  become  heated  or  cooled  much  more 
quickly  than  expanses  of  water.  Hence,  in  winter  the  continents  become  much  colder 
than  the  oceans,  and  are  therefore  the  seat  of  centers  of  high  barometric  pressure,  a  con¬ 
dition  exactly  the  reverse  of  that  prevalent  over  the  comparatively  warm  oceans.  From 
the  continental  areas  of  high  pressure  the  winds  tend  to  blow  outward,  especially  toward 
the  east  and  south.  Thus  the  cold  waves  of  the  Eastern  and  Southern  States  arise,  for 
on  the  western  side  of  ordinary  cyclonic  storms  the  indraft  of  air  occasioned  by  the  storms 
themselves  is  strengthened  by  the  general  high  pressure  prevaihng  in  the  cold  interior  of 
the  continent.  Inasmuch  as  Arizona  and  New  Mexico,  unlike  the  parts  of  India  with  which 
we  have  compared  them,  are  not  protected  by  an  east-and-west  range  of  mountains  such 
as  the  Himalayas,  chill  winds  from  the  north  sweep  over  the  country  in  winter,  producing 
frequent  frosts.  Even  as  far  south  as  Tucson,  in  latitude  32°  and  at  an  elevation  of  only 
2,300  feet  above  sea  level,  the  thermometer  occasionally  falls  to  16°  F.  Except  in  the 
warmest  and  lowest  places,  such  as  the  Gila  Valley  around  Phoenix,  or  at  Yuma  on  the 
Colorado  River,  this  liability  to  sudden  cold  prevents  the  growth  of  subtropical  fruits,  such 

9 


10 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


as  oranges,  although  much  farther  north  in  California  these  grow  to  perfection.  Oddly 
enough,  the  warmth  of  the  winter  in  the  intervals  between  cyclonic  storms,  when  north  winds 
do  not  prevail,  is  almost  as  fatal  to  such  northern  fruits  as  apricots  and  peaches  as  is  the 
low  temperature  to  oranges.  Since  this  is  a  desert  region  of  clear  skies  and  slight  humidity, 
the  daily  extremes  of  temperature  are  naturally  great,  amounting  often  to  40°.  In  Febru¬ 
ary,  or  even  January,  it  is  not  uncommon  for  the  mercury  to  rise  to  70°  F.,  and  if  the  nights 
are  above  the  freezing-point  the  fruit  trees  are  stimulated  to  open  their  blossoms  too  early. 
A  blighting  wind  from  the  north  swoops  down,  and  the  flowers  are  nipped. 

In  summer  the  conditions  are  the  reverse  of  those  of  winter,  except  that  the  range  of 
temperature  from  day  to  night  is  still  extreme.  The  whole  continental  interior  becomes 
greatly  heated  and  in  Tucson  the  temperature  rises  occasionally  to  114°  F.,  and  at  Yuma 
still  higher.  Under  such  circumstances  low  barometric  pressure  must  of  necessity  prevail, 
and  winds  from  the  periphery  of  the  continent  tend  to  blow  inward.  This  tendency  is  so 


Fig.  1. — Rainfall  of  Arizona  and  New  Mexico.  The  figures  show  annual  rainfall  in  inches. 
From  two  maps  published  in  Bull.  No. 188,  Bureau  of  Plant  Industry,  U.  S.  Dept.  Agriculture. 


strong  that  toward  the  end  of  June  the  trade  winds,  which  would  normally  be  expected  in 
the  district  from  Arizona  southward,  are  entirely  destroyed.  They  prevail  in  normal 
fashion  over  the  adjacent  oceans,  but  on  the  continent  they  give  place  to  somewhat  irregular 
winds  whose  prevailing  direction  is  distinctly  northward.  They  form,  as  it  were,  an  inward 
draft  blowing  from  the  Gulf  of  California  and  the  Pacific  Ocean  on  the  one  hand,  and 
from  the  Gulf  of  Mexico  on  the  other,  toward  the  continental  center  of  low  pressure. 
In  all  essential  respects  they  are  like  the  monsoons  of  India,  although  less  strong  and 
distinct  because  of  the  smaller  size  of  the  continent.  As  the  American  monsoons  approach 
the  land,  the  first  tendency  is  for  them  to  become  heated  and  hence  relatively  dry,  for  the 
land  is  hotter  than  the  ocean,  and  in  many  places  the  height  of  the  mountains  is  too  slight 
to  overcome  the  heating  due  to  the  land.  The  case  is  like  that  of  the  plains  of  Sind  at  the 
mouth  of  the  Indus.  As  the  winds  blow  inward,  however,  they  are  soon  forced  to  rise  by 
the  mountains,  they  reach  more  northerly  and  hence  cooler  latitudes,  and  they  enter  the 
continental  area  of  low  pressure  where  the  general  tendency  of  atmospheric  movements 


THE  MONSOON  CLIMATE  OF  ARIZONA  AND  NEW  MEXICO. 


11 


is  upward.  Thus  in  the  peninsula  of  Lower  California,  in  the  Mexican  states  of  Sonora  and 
Chihuahua,  and  in  Arizona  and  New  Mexico,  the  summer  is  characterized  by  heavy 
thunder-showers  of  the  kind  commonly  known  as  tropical.  These  usually  occur  from  about 
the  end  of  June  to  the  early  part  of  September,  beginning  earlier  and  ending  later  in  the 
south  than  in  the  north.  Thus  the  country  has  two  rainy  seasons,  one  in  winter  deriving 
its  rain  from  cyclonic  westerly  storms,  and  one  in  the  summer  deriving  rain  from  southerly 
monsoon  thunder-storms. 

The  total  rainfall  is  small,  ranging  from  5  to  20  inches  per  year  in  most  parts  of  the 
area,  as  is  shown  in  the  map,  figure  1,  and  rising  above  20  inches  only  in  the  high  mountains. 
The  variation  from  year  to  year,  however,  is  great,  as  may  be  seen  in  figure  2,  where  the 
rainfall  of  Tucson  is  plotted  by  calendar  years.  The  rainfall  of  the  two  seasons,  summer 
and  winter,  is  still  more  variable,  a  fact  evident  from  figure  3.  The  average  of  the  winter 
season  at  Tucson  is  4.5  inches.  The  amount  is  small  because  the  moisture  comes  largely 
from  the  Pacific  and  must  cross  the  high  Sierras  on  the  way.  The  winds,  of  course, 
often  blow  from  the  east  at  the  actual  time  of  rainfall,  but  this  affords  no  indication  of  the 
source  of  the  moisture.  In  all  cyclonic  storms  of  the  northern  hemisphere  the  motion  of 
the  air  around  and  toward  the  centers  of  low  pressure  is  similar,  and  the  southeastern 
quadrant  of  a  cyclonic  area  lying  in  front  of  the  storm  where  the  air  has  not  yet  suffered 
depletion  of  its  moisture,  and  where  the  winds  move  rapidly  from  warmer  to  cooler  lati¬ 
tudes,  is  apt  to  have  a  rainfall  more  abundant  than  that  of  any  other  quadrant.  Much 
of  the  rain  which  accompanies  such  winds  has  doubtless  come  from  the  oceans  to  the 
eastward,  but  more  has  probably  been  brought  by  the  prevailing  westerly  winds  and  is 
merely  caught  up  and  prepared  for  precipitation  by  the  easterly  winds. 

Inches  68  1870  72  74  76  78  1880  82  84  86  88  1890  92  94  96  98  1900  02  04  06  08  1910 


3017 

I 


Fig.  2. — Annual  Rainfall  at  Tucson,  Arizona,  1868-1912. 

The  paucity  of  the  winter  rainfall  would  not  be  so  harmful  were  it  not  for  its  extreme 
variability.  In  the  winter  of  1903-4  the  total  precipitation  at  Tucson  for  the  six  months 
from  November  to  April,  inclusive,  amounted  to  only  1.08  inches,  while  in  the  succeeding 
year  it  amounted  to  14.74.  Records  kept  at  Tucson  and  at  the  neighboring  army  post  of 
Fort  Lowell  show  that  in  the  years  from  1868  to  1912  the  winter  rainfall  was  less  than  2.5 
inches,  or  practically  useless,  in  9  winters;  it  amounted  to  from  2.5  to  5  inches,  that  is, 
it  was  fair,  in  20  winters;  it  ranged  from  5  to  7.5  inches,  or  was  good,  in  13  winters,  and 
exceeded  7.5  inches  only  three  times.  (See  table  la.)  These  figures  do  not  show  quite 
the  true  state  of  affairs  so  far  as  agriculture  is  concerned,  for  3  inches  in  February  and 
March,  after  the  chief  frosts  are  over,  are  worth  double  that  quantity  in  November  and 
December.  Still,  the  figures  serve  to  give  an  idea  of  the  extreme  variability  and  uncer¬ 
tainty  of  the  winter  rains.  Manifestly,  even  with  the  help  of  irrigation,  the  prospects  of 
the  farmer  are  not  of  the  rosiest  when  he  may  have  only  one-fourteenth  as  much  rain  in 
one  year  as  in  another. 

After  the  dry  spring  season  —  the  fore-summer,  as  MacDougal  has  called  it* —  the 
southerly  monsoon  gradually  becomes  well  established  by  the  strong  indraft  toward  the 
heated  continent,  and  thunder-showers  finally  begin  upon  the  mountains.  Far  to  the  south 
in  Mexico  the  first  showers  may  come  in  May  or  even  April.  In  southern  Arizona  they 
usually  begin,  as  we  have  seen,  toward  the  end  of  June  or  early  in  July,  while  farther  north 


*  D.  T.  MacDougal;  Botanical  Features  of  North  American  Deserts.  Cam.  Inst.  Wash.  Pub.  99,  1908. 


12 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


they  do  not  come  till  mid-July.  In  exceptionally  warm  years,  however,  they  may  begin 
unusually  early  because  of  the  more  rapid  heating  of  the  continent.  Thus  in  1910  the  mean 


temperature  of  the  month  of  May  at  Tucson  was  6°  F.  above  the  average  of  the  preceding 
four  years ;  and  showers,  light  on  the  plains,  but  heavy  on  the  mountains,  began  early  in 
June.  Farther  north,  where  the  showers  begin  later,  they  also  end  earlier,  and  instead  of 
lasting  into  September,  terminate  in  August.  Everywhere  they  are  accompanied  by  vivid 
lightning  and  the  rainfall  is  torrential. 

The  summer  rains  are  more  abundant  and  less  vari¬ 
able  than  those  of  the  winter.  At  Tucson  they  average 


Table  1a. — Summer  and  Winter  Rain¬ 
fall  at  Tucson  (and  Fort  Lowell) 
from  1868  to  1912. 


7.14  inches  for  the  six  months  from  May  to  October  inclu¬ 
sive.  During  the  45  years  embraced  in  the  records  at 
Tucson  and  Fort  Lowell  the  minimum  was  3.01  inches 
in  1885  and  3.03  in  1900,  while  the  maximum  was  14.2 
inches  in  1876.  Fifteen  summers  had  a  rainfall  of  less 
than  5  inches,  12  from  5  to  7.5  inches,  9  from  7.5  to  10 
inches,  and  9  over  10  inches.  The  summer  showers  are  so 
sudden  and  the  rain  falls  so  rapidly  that  a  large  part  of 
the  water  runs  off  in  great  floods,  serving  no  useful  pur¬ 
pose.  Nevertheless,  the  showers  support  considerable 
vegetation,  and  from  the  earhest  times  have  enabled  the 
inhabitants  to  cultivate  quickly  growing  crops  like  corn 
and  beans,  but  neither  these  nor  any  other  crops  can  be 
grown  without  irrigation  except  in  a  few  places  at  great 
altitudes;  yet  in  these  places  there  is  always  danger  of 
failure.  Even  with  the  aid  of  irrigation  the  arable  area 
is  at  best  extremely  limited.  The  division  of  the  rainfall 
into  two  seasons  has,  as  we  shall  see,  a  beneficial  effect 
upon  native  vegetation,  but  it  can  scarcely  be  considered 
particularly  advantageous  to  agriculture,  especially  to  the 
type  brought  by  the  inhabitants  of  Europe  to  the  better- 
watered  parts  of  the  United  States. 

From  a  theoretical  standpoint  the  rainfall  of  Arizona 
and  New  Mexico  is  peculiarly  interesting  because  the 
winter  rains  possess  the  characteristics  of  the  temperate 
zone  and  the  summer  rains  those  of  equatorial  regions. 

It  is  not  possible  to  enter  into  any  detailed  discussion  of 
the  subject  at  this  time,  but  one  or  two  matters  may  be 
pointed  out  as  especially  deserving  of  study.  In  the  first 
place,  at  high  elevations  among  the  mountains  the  sea¬ 
sonal  distribution  of  precipitation  is  not  the  same  as  in 
the  lowlands.  For  instance,  on  the  Santa  Catalina  Mountains,  over  9,000  feet  in  eleva¬ 
tion,  Dr.  MacDougal  has  found  not  only  that  the  rainfall  is  two  or  three  times  as  large 
as  down  below,  as  might  be  expected,  but  also  that  the  winter  rains  are  heavier  than  those 
of  summer.  This,  of  course,  is  the  reverse  of  what  prevails  in  the  lowlands.  It  seems  to 
mean  that  the  climate  of  the  mountains  approximates  to  that  of  regions  farther  north,  not 
only  in  temperature,  but  in  the  character  of  its  storms.  In  other  words,  it  seems  as  if 
westerly  winds  and  their  attendant  conditions  prevailed  for  a  longer  time,  or  else  during 
the  same  time,  but  more  completely  at  high  levels  than  at  low,  while  in  the  districts  of 
lower  altitude  equatorial  conditions  are  predominant  so  far  as  precipitation  is  concerned. 
To  put  the  matter  in  another  way,  it  may  be  that  the  heating  up  of  the  continent  in 
summer  disturbs  the  equilibrium  in  the  upper  air  so  much  less  than  in  the  lower  that 


[See  Figures  3  and  4]. 


Summer 
of — 

Inches  of 
rainfall. 

Winter 
of — 

Inches  of 
rainfall. 

1868 

8.19 

1867-  68 

4.43 

1869 

9.48 

1868-  69 

4.10 

1870 

4.86 

1869-  70 

2.25 

1871 

7.12 

1870-  71 

2.10 

1872 

11.48 

1871-  72 

1.27 

1873 

3.43 

1872-  73 

3.09 

1874 

7.90 

1873-  74 

7.31 

1875 

8.90 

1874-  75 

2.97 

1876 

14.20 

1875-  76 

2.20 

1877 

6.37 

1876-  77 

4.21 

1878 

11.16 

1877-  78 

6.42 

1879 

4.29 

1878-  79 

5.80 

1880 

4.88 

1879-  80 

5.07 

1881 

12.64 

1880-  81 

2.66 

1882 

10.27 

1881-  82 

4.35 

1883 

4.57 

1882-  83 

4.08 

1884 

4.47 

1883-  84 

6.53 

1885 

3.01 

1884-  85 

5.88 

1886 

4.27 

1885-  86 

4.32 

1887 

10.69 

1886-  87 

2.08 

1888 

4.25 

1887-  88 

3.34 

1889 

11.50 

1888-  89 

8.98 

1890 

10.66 

1889-  90 

5.14 

1891 

3.93 

1890-  91 

5.75 

1892 

4.05 

1891-  92 

5.56 

1893 

9.95 

1892-  93 

2.50 

1894 

3.12 

1893-  94 

3.24 

1895 

6.14 

1894-  95 

2.26 

1896 

9.33 

1895-  96 

5.38 

1897 

8.66 

1896-  97 

3.06 

1898 

7.46 

1897-  98 

3.32 

1899 

5.66 

1898-  99 

4.64 

1900 

3.03 

1899-1900 

2.87 

1901 

7.43 

1900-  01 

5.66 

1902 

4.14 

1901-  02 

1.06 

1903 

5.80 

1902-  03 

6.23 

1904 

6.12 

1903-  04 

1.08 

1905 

5.85 

1904-  05 

14.74 

1906 

4.78 

1905-  06 

7.17 

1907 

10.88 

1906-  07 

7.77 

1908 

7.92 

1907-  08 

4.01 

1909 

7.19 

1908-  09 

4.13 

1910 

7.22 

1909-  10 

2.88 

1911 

7.58 

1910-  11 

4.42 

1912 

6.68 

1911-  12 

3.76 

THE  MONSOON  CLIMATE  OF  ARIZONA  AND  NEW  MEXICO. 


13 


the  rainfall  at  high  altitudes  is  influenced  much  less  than  at  low.  As  yet,  data  obtained 
on  the  subject  are  not  sufiBcient  to  permit  of  any  trustworthy  conclusions.  The  matter 
is  mentioned  here  merely  as  one  of  the  many  interesting  problems  which  would  repay 
investigation. 

Another  problem  of  the  same  kind  is  illustrated  in  figures  2  and  3.  The  curve  of 
figure  2  represents  the  total  rainfall  by  years  from  1868  to  1912  as  given  in  the  Summary 
of  the  Climatological  Data  for  the  United  States  and  in  the  Monthly  Weather  Review. 
Figure  3  shows  the  summer  rainfall  for  the  six  months  from  May  to  October  inclusive  and 
the  winter  rainfall  for  the  six  months  from  November  to  April  during  the  same  term  of 
years.  The  latter  two  curves  seem  to  indicate  a  reciprocal  relation  of  some  sort  between 
the  rainfall  of  summer  and  winter.  In  general,  when  the  summer  rains  increase  in  amount 
the  winter  rains  decrease,  and  vice  versa.  This  phenomenon  is  not  confined  to  Tucson, 
but  is  apparently  characteristic  of  the  Southwest  as  a  whole.  For  instance,  in  the  two 
curves  at  the  lower  left-hand  corner  of  figure  11,  on  page  109,  it  is  clearly  seen  in  the  rain¬ 
fall  of  Flagstaff,  200  miles  north  of  Tucson  and  5,000  feet  higher.  Inasmuch  as  a  similar 
relation  between  the  rainfall  of  equatorial  and  -temperate  regions  has  been  inferred  from 


Summer  rainfall 
Winter  rainfall 


Fig.  3. — Winter  and  Summer  Rainfall  at  Tucson,  Aiizona,  1808-1912. 
- Winter  rainfall,  Nov  .-Apr.  - -  Summer  rainfall,  May-Oct. 


68  1870  72  74  76  78  1880  82  84  86  88  1890  92  94  96  98  1900  02  04  06  08  1910 


Fig.  4. — Comparison  of  3-year  Means  of  Winter  and  Summer  Rainfall  at  Tucson,  Arizona,  1868-1912. 


the  comparison  of  records  in  various  parts  of  the  world,  particularly  India,  it  is  of  great 
interest  to  find  it  so  clearly  manifest  here.  Examination  of  the  curves  shows  that  in  two 
cases  out  of  every  three  a  minimum  of  winter  rain  is  followed  by  a  maximum  during  the 
succeeding  summer.  One  would  expect  to  find  the  reverse  also  true,  and  that  a  summer 
maximum  would  be  followed  by  a  winter  minimum,  but  this  does  not  hold  good.  A 
summer  minimum,  however,  is  usually  followed  by  a  winter  maximum.  In  other  words, 
if  it  be  permissible  to  generalize  on  so  small  a  basis  of  fact,  the  minima  appear  to  be  the 
critical  points.  A  maximum,  either  in  summer  or  winter,  is  not  likely  to  be  followed  by 
especially  marked  conditions  in  the  succeeding  season.  A  minimum,  on  the  contrary, 
whether  in  summer  or  winter,  is  likely  to  be  followed  immediately  by  a  maximum  in  the 
succeeding  season. 

The  preceding  generalization  obviously  holds  good  only  about  two-thirds  of  the  time. 
In  figure  4  the  summer  and  winter  curves  have  been  smoothed  by  using  3-year  means 
instead  of  the  actually  observed  rainfall.  When  the  minor  fluctuations  are  thus  eliminated, 
the  opposed  phases  of  the  summer  and  winter  curves  are  brought  out  clearly  in  the  period 
from  1868  to  1887,  and  less  clearly  from  1895  to  1907.  In  the  period  from  1888  to  1894 


14 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  diagram  presents  a  wholly  different  appearance:  the  two  curves  show  agreement 
instead  of  opposition.  The  effect  of  such  agreement  upon  the  economic  life  of  the  country 
is  marked.  During  the  late  eighties,  when  both  summer  and  winter  rains  were  on  the 
increase,  the  cattle  industry  flourished  as  at  no  other  period.  In  the  early  nineties,  how¬ 
ever,  when  the  rain  of  both  seasons  decreased,  dire  distress  prevailed.  Cattle  died  by  the 
thousand  and  the  industry  received  such  a  blow  that  on  many  ranches  there  are  now 
only  hundreds  of  animals  where  then  there  were  thousands.  The  peculiar  fashion  in 
which  the  summer  and  winter  curves  show  opposite  phases  part  of  the  time,  and  then 
suddenly  agree,  suggests  various  speculations  as  to  the  cause.  It  looks  as  if  there  might 
be  more  than  one  type  of  cyclical  or  periodic  variation  in  the  activity  of  the  earth’s  at¬ 
mosphere.  One  type  perhaps  causes  agreement  and  one  type  disagreement.  Here,  as 
in  the  case  of  the  contrast  between  the  precipitation  of  high  and  low  regions,  it  is  too  early 
to  attempt  to  form  positive  theories. 


CHAPTER  II. 

THE  TOPOGRAPHIC  INFLUENCE  OF  ARIDITY. 


In  the  modern  science  of  physiography  as  developed  in  recent  years,  under  the  leader¬ 
ship  of  Professor  Davis,  one  of  the  most  interesting  features  is  the  connection  between 
the  form  of  the  earth’s  surface  and  the  climate  of  any  given  region.  Not  only  do  glaciated 
areas  possess  their  own  peculiar  topography,  but  so  do  humid  and  dry  regions.  The  scenery 
of  Arizona  and  New  Mexico  is  stamped  indelibly  with  the  impress  of  an  aridity  which 
has  lasted  hundreds  of  thousands  of  years.  Just  when  it  began  we  can  not  tell,  but 
certainly  far  back  in  the  Tertiary  era,  and  possibly  earlier,  for  deposits  characteristic  of 
aridity  not  only  attain  a  great  thickness  superficially,  but  are  interbedded  with  marine 
strata  in  formations  dating  far  back  in  geological  time.  A  full  discussion  of  the  effects  of 
aridity  upon  the  form  of  the  land  in  all  parts  of  New  Mexico  and  Arizona  would  require  a 
volume  and  would  demand  an  amount  of  field  work  far  greater  than  I  have  been  able  to 
give  to  the  matter.  Accordingly,  in  the  following  pages  I  shall  limit  myself  to  a  few  salient 
features  which  clearly  show  evidences  of  aridity,  or  are  of  special  importance  in  relation 
to  changes  of  climate  and  the  ancient  human  occupation  of  the  country. 

Topographically  Arizona  and  New  Mexico  consist  of  two  chief  parts,  plateaus  of  nearly 
horizontal  strata  5,000  to  7,000  feet  high  and  basin  regions  where  mountain  ranges,  due  to 
faulting  or  to  rapid  uplift  of  relatively  small  areas,  alternate  with  more  or  less  completely 
inclosed  basins  filled  with  alluvial  waste.  In  Arizona  the  plateaus  and  the  basin  ranges  are 
sharply  separated  by  the  Mogollon  Escarpment,  a  line  of  southward-facing  cliffs  which 
extend  approximately  northwest  and  southeast  across  nearly  the  whole  State  and  pass 
almost  through  its  center.  North  of  the  escarpment  lies  a  high  plateau  broken  in  places 
by  fault  scarps  running  north  and  south,  diversified  by  extinct  volcanoes  and  cut  by  deep 
canyons,  like  that  of  the  Colorado,  but  preserving  almost  uniformly  the  practically  level 
position  of  its  rock  formations  in  spite  of  thousands  of  feet  of  uplift  since  their  original 
deposition.  South  of  the  escarpment  the  basin-range  region  lies  at  a  general  elevation 
3,000  or  4,000  feet  less  than  that  of  the  plateaus.  Here  the  strata  by  no  means  lie  hori¬ 
zontal,  but  have  been  tipped  this  way  and  that,  chiefly  by  means  of  block  faulting  along 
lines  running  more  or  less  closely  north  and  south.  The  spaces  intervening  between  the 
uplifted  blocks  form  basins  which  have  been  filled  with  alluvium.  Thus  to  the  eye  of  the 
traveler  the  difference  between  the  plateaus  and  the  plains  may  be  briefly  summed  up  by 
saying  that  the  plateaus  are  a  region  of  great  plains  cut  by  deep  canyons,  while  the  basin- 
range  country  is  composed  of  great  plains  broken  by  narrow  mountain  ranges.  In  New 
Mexico  the  separation  between  the  plateaus  and  the  basin  ranges  is  not  so  distinct  as  in 
Arizona.  In  the  elevated  regions  of  the  northwest,  however,  and  in  the  Staked  Plains  of 
the  eastern  part  of  the  State  the  plateau  quality  is  as  well  marked  as  in  Arizona,  while 
basins  and  ranges  of  mountains  due  to  faulting  are  almost  as  characteristic  a  feature  in 
the  south  as  in  the  neighboring  State  to  the  west.  In  the  center,  especially  toward  the 
north  near  Colorado,  the  main  chain  of  the  Rocky  Mountains  extends  down  into  New 
Mexico  and  adds  a  distinct  type  of  topography.  The  mountains,  however,  soon  break  up 
into  isolated  ranges  rising  from  the  plateau  or  bordering  waste-filled  basins,  so  that  most 
of  the  country  may  fairly  be  said  to  belong  to  one  of  the  two  main  types  with  which  we  are 
dealing.  Inasmuch  as  the  main  chain  of  the  Rockies  has  little  to  do  either  with  the  early 
inhabitants  or  with  the  other  evidences  of  climatic  changes  with  which  we  are  here  con¬ 
cerned,  it  will  not  be  further  discussed. 


15 


16 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


THE  TOPOGRAPHIC  FEATURES  OF  THE  PLATEAUS. 

(1)  Mature  Uplands. — Where  most  typically  developed  the  plateaus  present  three 
chief  types  of  topographic  form,  which  may  be  described  as  mature  uplands  of  ancient 
origin,  young  plains  of  erosion  upon  soft  strata,  and  young  cliffs  composed  of  hard  strata 
and  forming  the  borders  either  of  mesas  or  canyons.  Other  features,  such  as  volcanic 
cones  or  fault  scarps,  for  example,  may  be  omitted  as  of  secondary  importance  in  spite  of 
their  great  interest.  The  plateaus,  it  is  needless  to  say,  were  formed  by  the  slow  uplifting 
of  large  areas  of  the  earth’s  surface  without  any  pronounced  tilting  or  bending  of  the  rocks. 
In  all  such  cases  an  old  topography,  brought  to  a  greater  or  less  degree  of  maturity,  must 
have  been  carried  up  to  a  height  far  above  that  under  which  it  was  originally  developed. 
In  some  cases — for  example,  the  Kaibab  Plateau  in  northern  Arizona  just  north  of  the 
part  of  the  Grand  Canyon  most  commonly  visited— this  ancient  topography  is  still  pre¬ 
served.  On  the  edges  it  is  being  rapidly  dissected  and  removed  by  the  rapid  streams 
which  are  the  normal  result  of  uphft.  The  Mescalero  Plateau,  east  of  the  Otero  Basin 
in  the  south  central  part  of  New  Mexico,  is  another  good  example.  Here  a  steep  fault 
scarp,  gashed  by  precipitous  young  canyons,  rises  on  the  east  side  of  the  basin  to  a  height 
of  about  9,000  feet,  nearly  5,000  feet  above  the  basin  floor.  At  the  top  one  emerges  from 
the  narrow  valleys  formed  since  the  last  uplift  and  finds  himself  in  a  wooded  region  of 
open,  mature  topography.  Gentle  slopes  rise  from  broad  valleys  to  round-topped  hills  of 
nearly  uniform  height.  Everywhere  the  soil  is  deep,  and  outcrops  of  naked  rock  are  rare. 
Often  the  valleys  converge  into  flat  sink-holes,  where  the  water  stands  for  a  while  before 
it  can  seep  away  through  underground  passages  in  the  soluble  limestone.  Everything 
indicates  that  the  region  was  subjected  to  extensive  erosion  long  before  it  was  slowly 
upheaved  to  its  present  situation.  Its  topography  was  formed  under  conditions  quite 
different  from  those  of  to-day,  and  we  can  as  yet  draw  no  satisfactory  conclusion  as  to  the 
climate  prevalent  during  the  long  ages  required  for  its  erosion. 

(2)  Young  Plains  due  to  Erosion. — The  mature  uplands  are  in  most  cases  so  elevated 
as  to  be  too  cold  for  extensive  habitation  or  agriculture.  On  their  borders,  however,  the 
processes  of  erosion  have  in  many  cases  given  rise  to  broad  and  relatively  youthful  plains 
of  subaerial  denudation  at  altitudes  of  6,000  or  7,000  feet.  These  would  be  habitable 
if  provided  with  more  water,  and  many  of  them  seem  to  have  been  cultivated  in  former 
times.  The  plains  are  rarely  smooth  for  any  great  distance.  At  frequent  intervals  they  are 
interrupted  by  steep-sided  mesas,  hues  of  cliffs,  or  canyons,  the  product  of  the  same  pro¬ 
cess  of  erosion  which  has  produced  the  plains.  It  is  unnecessary  here  to  enter  into  any 
detailed  description  of  this  well-known  process.  I  would  merely  call  attention  to  the 
fact  that  it  reaches  a  high  state  of  development  only  in  arid  regions.  Where  strata  of 
unequal  hardness  are  exposed  to  erosion,  such  soft  materials  as  shales  are  worn  back 
much  faster  than  hard  formations,  such  as  massive  sandstones  or  limestones.  If  the  strata 
are  horizontal  the  weathering  of  the  soft  formation  tends  to  carry  it  away  from  under 
the  hard  formation  wherever  a  vertical  surface  is  exposed  by  erosion.  The  hard  rocks  of 
course  break  off  as  soon  as  they  are  undermined,  and  thus  steep  cliffs  are  formed.  This 
process  takes  place  in  a  moist  chmate  quite  as  much  as  in  a  dry,  but  it  can  not  go  so  far. 
In  the  moist  climate  two  things  tend  to  check  it.  In  the  first  place,  the  action  of  frost, 
rain,  snow,  and  vegetation  tends  to  cause  the  weathering  of  the  hard  rocks  to  go  on  at  a 
rate  which  approximates  that  of  the  soft  rocks  more  nearly  than  in  dry  regions.  Hence  rela¬ 
tively  more  talus  falls  from  the  cliffs  of  moist  regions  than  from  those  of  dry  regions,  and  the 
tops  of  the  cliffs  are  worn  back,  while  the  soft  strata  at  the  base  are  protected  by  the  accu¬ 
mulation  of  d6bris.  Hence  steep  cliffs  are  not  common.  In  the  second  place,  erosion  is  less 
hindered  in  dry  regions  than  in  wet.  The  torrential  character  of  the  rains  and  the  absence 
of  vegetation  allow  the  talus  to  be  carried  rapidly  away  in  arid  countries,  while  the  barren- 


THE  TOPOGRAPHIC  INFLUENCE  OF  ARIDITY. 


17 


ness  and  dryness  of  the  surface  allow  the  wind  to  etch  out  the  soft  rocks  in  a  fashion  quite 
unknown  in  moist  lands.  Consequently,  where  strong  contrasts  of  hardness  exist  in  a  dry 
climate  the  soft  rocks  may  be  worn  back  for  miles,  leaving  the  underlying  hard  rocks  to  form 
broad  plains  of  erosion,  while  the  remnants  of  the  overlying  hard  rocks  form  mesas.  Where 
the  climate  is  moist  the  sharp  contrast  between  the  hard  rocks  and  the  soft  is  diminished, 
as  we  have  seen.  Moreover,  the  number  of  residual  hills  of  hard  rock  is  likely  to  be  large 
because  of  the  abundance  of  streams  and  consequent  minute  dissection.  Thus  the  plains 
of  erosion  are  apt  to  be  more  broken  by  hills  than  in  dry  regions,  while  the  slopes  are 
gentler  because  more  masked  by  talus. 

(3)  Cliffs  bordering  Mesas  and  Canyons. — The  origin  of  the  steep  cliffs  of  the  plateau 
country  is  evident  from  what  has  just  been  said.  The  uplifting  of  the  plateaus  has  caused 
rapid  erosion  and  the  swift  deepening  of  valleys.  The  differences  between  hard  and  soft 
strata  have  resulted  in  a  benched  topography;  the  hard  layers  form  cliffs  while  the  soft 
wear  back  so  as  to  form  benches  on  top  of  the  hard.  Where  the  chffs  wear  back  far  from 
the  streams,  leaving  plains,  the  hard  formations  may  still  retain  their  steepness,  and  thus 
mesas  and  buttes  arise.  For  our  present  purpose  this  is  important,  partly  because  such 
topography  is  characteristic  of  arid  regions,  and  still  more  because  of  its  relation  to  human 
occupation.  The  ancient  chff-dwellers,  who  figure  so  largely  in  American  archeology, 
made  most  of  their  dwellings  in  narrow  canyons  just  at  the  point  where  the  lowest  soft 
layer  makes  a  hollow  under  the  overlying  hard  layer.  Starting,  probably,  with  no  shelter 
except  that  of  the  cliffs  overhanging  their  wind-scoured  caves,  they  gradually  learned  to 
dig  caves  in  soft  formations  such  as  the  volcanic  tuff  of  the  Pajarito  Plateau  near  Sante  Fe 
in  northern  New  Mexico,  while  later  they  developed  the  art  of  building  walls  in  front  of 
the  caves,  and  these  in  turn  led  them  to  build  entire  rooms,  sometimes  three  or  four  rows 
deep,  at  the  base  of  the  chffs.  Others  among  the  ancient  Americans  utilized  these  same 
cliffs  for  protection,  building  their  houses  of  stone  on  the  tops  of  great  steep-sided  mesas, 
of  which  the  Mesa  Verde  is  the  best  known.  Many  of  the  ancient  inhabitants,  as  may 
be  seen  near  the  remarkable  ruins  of  the  Chaco  Canyon  in  northwestern  New  Mexico, 
dwelt  at  the  base  of  the  cliffs,  but  apparently  cultivated  the  plains  of  erosion  high  above 
their  heads.  This  last  matter  is  still  in  dispute,  but  there  can  be  no  question  that  the 
peculiar  topography  characteristic  of  arid  plateaus  was  the  warp  upon  which  was  woven 
one  of  the  most  interesting  of  all  the  phases  of  pre-Columbian  American  civilization. 

THE  BASIN  REGIONS. 

(1)  The  Mountain  Slopes. — Going  down  from  the  plateaus  to  the  basin  regions  of  the 
south,  we  find  a  country  where,  during  the  most  ancient  times,  men  dwelt  as  numerously 
as  in  the  plateaus,  although  the  remaining  ruins  are  less  conspicuous.  Here,  as  there, 
three  chief  elements  of  physiographic  form  dominate  the  landscape:  (1)  rough,  rocky 
mountain  slopes,  usually  of  steep  ascent;  (2)  gently  sloping  piedmont  deposits  of  gravel 
merging  imperceptibly  into  smooth  plains  and  playas  of  fine  silt;  and  (3)  terraces  com¬ 
posed  of  alluvium,  chiefly  in  the  form  of  gravel.  For  convenience  I  shall  not  attempt  a 
general  description  of  these  elements,  but  shall  describe  them  as  they  occur  in  the  region 
of  Tucson,  where  much  of  our  future  investigation  will  center.  This  will  serve  as  well  as 
a  more  general  description,  for  in  all  essential  matters  there  is  little  difference  between  the 
various  parts  of  the  basin  region. 

Near  Tucson  the  mountain  slopes,  the  first  of  our  three  physiographic  elements,  form  the 
sides  of  irregular  ranges  scattered  here  and  there  like  islands  in  the  midst  of  a  sea  of  gravel 
and  silt.  In  general  the  mountains  run  northwest  and  southeast.  They  vary  in  height 
from  4,000  to  9,000  feet,  while  the  plains  lie  at  an  altitude  of  2,000  to  3,000  feet,  dimin¬ 
ishing  to  the  west  and  increasing  to  the  east  in  New  Mexico.  Some  ranges,  such  as  the 
Santa  Catalinas  northeast  of  Tucson,  the  Tortolitas  farther  to  the  north,  and  the  Sierritas 

3 


18 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


to  the  southwest,  are  of  disordered  structure  and  consist  of  masses  of  granites  and  gneisses 
flanked  by  sedimentary  rocks  of  Paleozoic  or  later  age.  The  majority  of  the  ranges, 
however,  are  composed  of  Paleozoic  sedimentary  or  metamorphic  rocks,  together  with 
later  lavas.  Most  are  fault  blocks  which  have  been  uplifted  on  the  southwest  side  of  lines 
of  faulting  running  northwest  and  southeast,  and  have  been  tilted  in  such  a  way  that  the 
back  of  the  block  slopes  toward  the  southeast.  The  structure  is  not  regular,  for  there 
has  been  a  large  amount  of  secondary  faulting.  As  none  of  the  faulting  is  recent,  the 
mountains  are  maturely  dissected.  This  does  not  mean  that  sharp  forms  of  peak  and 
cliff  are  rare.  On  the  contrary,  many  of  the  fault-block  ranges  are  carved  into  the  most 
striking  forms,  and  all  the  mountains  display  a  great  amount  of  naked  rock.  The  little 
Tucson  Range,  for  instance,  which  lies  just  to  the  west  of  Tucson,  and  is  composed  largely 
of  andesite  and  other  eruptives,  presents  one  of  the  most  jagged  sky-lines  to  be  found 
anywhere  in  America,  a  striking  sight  against  the  clear  sunset  sky.  The  Sawtooth  Moun¬ 
tains,  a  few  miles  to  the  west,  are  of  the  same  structure,  and  are,  if  anything,  still  more 
jagged.  The  granitic  mountains,  on  the  other  hand,  are  not  characterized  by  prominent 
peaks.  From  a  distance  they  present  the  appearance  of  great  solid  masses,  but  near  at 
hand  are  seen  to  be  full  of  splendid  deep  canyons,  often  with  precipitous  walls  of  naked  rock. 

The  rockiness  of  the  mountains  speaks  strongly  of  arid  climatic  conditions.  Mountains 
in  a  similar  stage  of  dissection  in  a  moist  climate  would  be  covered  with  soil  and  would 
present  graded  slopes  for  the  most  part.  In  Arizona  the  slopes  are  largely  washed  bare  of 
soil  because  lack  of  moisture  restricts  the  growth  of  plants  and  prevents  the  accumulation 
of  roots  and  fallen  leaves  which  would  hold  the  soil  in  place  when  heavy  showers  tend  to 
wash  it  down.  The  truth  of  this  statement  is  apparent  from  the  fact  that  the  low  mountains, 
under  5,000  feet  or  so  in  height,  are  more  rocky  and  on  the  whole  more  rugged  than  those 
which  rise  higher.  The  high  mountains,  such  as  the  Catalinas,  which,  as  we  have  seen, 
rise  to  a  height  of  9,000  feet,  enjoy  a  much  greater  rainfall  than  the  lower  portions  of  the 
country,  at  least  twice  as  much  apparently.  They  are  also  cooler,  so  that  evaporation  is 
far  less  active  than  in  the  hot  regions  of  lower  elevation.  Accordingly  the  supply  of 
moisture  available  for  plants  is  far  in  excess  of  that  below,  and  the  mountains  above  5,000 
feet  are  covered  with  forests.  At  the  lower  levels  oaks  and  bushy  trees  of  the  smooth- 
barked  manzanita  and  its  allies  prevail,  while,  higher  up,  the  mountains  are  densely  clothed 
with  splendid  forests  of  juniper  and  pine.  In  the  mountains  of  moist  lands  the  amount 
of  soil  commonly  decreases  from  the  bottom  upward.  In  southern  Arizona  the  case  is 
different;  from  the  base  of  the  hills,  at  an  elevation  of  approximately  3,000  feet,  the  amount 
of  soil  decreases  in  the  normal  fashion  at  first,  but  after  1,000  or  2,000  feet  it  begins  to 
increase,  and  at  a  height  of  6,000  or  7,000  it  is  much  greater  than  at  the  base.  Such  con¬ 
ditions  can  occur  only  in  an  arid  climate  among  mountains  rising  high  enough  to  receive  a 
considerable  rainfall. 

(2)  The  Bahadas,  or  Piedmont  Gravel  Deposits. — The  second  element  in  the  landscape 
in  the  basin  region  is  the  vast  accumulation  of  gravel,  sand,  and  silt  which  flanks  the 
mountains  on  every  side.  This  accumulation  of  detrital  material  slopes  gently  away, 
mile  after  mile,  becoming  flatter  and  flatter,  until  many  of  the  slopes  merge  into  level 
playas.  The  name  "bajada”  has  been  applied  to  such  slopes  by  Tollman.*  The  Span¬ 
iards  use  the  word  “bajada”  to  designate  any  sort  of  descent,  including  the  process  of 
descending,  but  in  the  absence  of  any  other  appropriate  term  in  English,  I  feel  constrained 
to  adopt  it.  The  word  is  pronounced  “bahadtha,”  the  sound  of  the  d  being  neither  d  nor 
th  exactly.  The  a’s  have  the  French  sound  and  the  accent  is  on  the  second  syllable.  In 
defiance  of  all  rules  I  venture  to  write  the  word  with  an  h  instead  of  a  j,  because  otherwise 
it  is  sure  to  be  mispronounced.  Genetically  it  belongs  to  the  same  class  as  mesa,  hutte, 
arroyo,  playa,  and  others  in  conunon  use. 


*  C.  F.  Tollman:  Erosion  and  Deposition  in  Southern  Arizona  Bolson  Region.  Jour.  Geol.,  vol.  xvii,  1909,  p.  142. 


THE  TOPOGRAPHIC  INFLUENCE  OF  ARIDITY. 


19 


The  bahadas  consist  primarily  of  innumerable  detrital  fans  deposited  by  the  streams 
at  the  point  where  they  issue  from  the  mountains.  In  moist  countries  such  fans  can  not 
attain  large  dimensions,  for  they  are  soon  washed  away  by  the  steady  flow  of  the  streams. 
In  dry  regions,  on  the  contrary,  they  tend  constantly  to  increase  in  size.  None  but  the 
largest  streams  are  permanent;  for  the  great  majority  come  to  an  end  soon  after  leaving 
the  constricted  valleys  of  the  mountains.  Emerging  from  the  uplands,  their  speed  is 
checked  so  that  they  deposit  their  load  of  waste  and  are  divided  into  many  distributaries. 
Thus  fans  are  formed  in  whose  thirsty  gravel  most  of  the  water  is  lost,  while  the  remainder 
runs  on  a  few  miles  farther  with  constantly  diminishing  volume  until  it  finally  spreads  out 
into  thin  sheets,  forming  playas  which  soon  evaporate.  Except  in  the  case  of  occasional 
floods  which  reach  the  main  streams  and  run  through  to  the  sea,  every  bit  of  material  that 
most  of  the  streams  bring  down  from  the  mountains  is  deposited  in  the  lowlands.  Thus 
year  by  year  and  century  by  century  the  fans  grow  in  size,  and  finally  coalesce  into  what 
appears  to  be  a  single  great  slope,  a  vast  apron  or  glacis  surrounding  all  the  mountains, 
and  ever  rising  higher  as  the  mountains  themselves  are  worn  lower.  In  time  the  waste 
from  the  higher  mountains  may  bury  the  lower  ones,  cutting  them  off  at  first  and  forming 
the  gravelly  passes  which  make  it  so  easy  to  cross  the  minor  ranges  at  frequent  intervals. 
As  time  goes  on,  many  small  mountains  are  so  buried  that  they  merely  stick  up  as  little 
pointed  buttes  in  the  midst  of  a  rising  sea  of  gravel  and  silt.  Doubtless  in  past  ages  many 
hills  have  disappeared  entirely,  for  the  deposits  washed  down  from  the  mountains  to  the 
lowlands  have  a  depth  of  over  1,000  feet  not  far  from  Tucson,  as  shown  by  the  records  of 
wells  dug  by  the  Southern  Pacific  Railroad.* 

Close  to  the  mountains  the  bahadas  consist  of  coarse  material  in  the  form  of  subangular 
boulders  with  a  matrix  of  cobbles  and  sand.  Farther  out,  as  the  slope  decreases,  the 
boulders  disappear,  although  in  some  cases  they  are  washed  to  a  distance  of  5  miles  or 
more.  Then  the  cobbles  diminish  in  size  and  finally  vanish,  leaving  only  gravel,  and  that 
in  turn  gradually  gives  place  to  the  fine  sand  and  silt  which  alone  are  found  in  the  playas 
where  the  slope  is  reduced  almost  to  zero  and  the  waters  come  to  rest.  The  bahadas, 
playas,  and  half-buried  mountains  of  the  southwestern  part  of  the  United  States  reproduce 
exactly  the  topographic  forms  of  other  deserts  in  distant  regions,  such  as  Syria,  Persia,  and 
western  China.  In  aU  parts  of  the  world  these  great  piedmont  deposits  preserve  full 
records  of  the  cHmatic  vicissitudes  to  which  they  have  been  subject.  Manifestly  the 
nature  of  the  materials  laid  down  under  various  conditions  of  climate  is  bound  to  vary, 
even  though  a  certain  degree  of  aridity  may  have  prevailed  at  all  times.  If  the  mountains 
were  at  some  time  denuded  of  trees  by  excessive  drought,  a  great  amount  of  soil  must 
have  been  washed  down  in  ensuing  years.  If  the  amount  of  vegetation  became  greater 
than  now,  and  the  streams  became  more  constant  by  reason  of  greater  rainfall,  deposition 
at  the  immediate  base  of  the  mountains  must  have  diminished,  while  farther  away  it  must 
have  increased.  Thus  the  depths  of  the  bahadas  must  preserve  a  record  of  all  manner 
of  changes.  In  the  present  volume  this  subject  will  not  be  taken  up,  because  it  does 
not  bear  upon  our  immediate  problem  of  recent  climatic  changes,  but  evidently  any  com¬ 
prehensive  study  of  the  climatic  conditions  of  the  geologic  past  demands  a  careful  examina¬ 
tion  of  complete  sections  from  the  bahada  slopes  not  only  of  America,  but  of  all  parts  of 
the  world. 

(3)  The  Terraces. — The  bahadas  by  no  means  always  merge  into  playas,  nor  do  they 
universally  coalesce  with  one  another.  In  fact,  they  usually  fail  to  do  so.  Once  all  the 
bahadas  coalesced  smoothly  and  merged  into  playas  or  flat  valley  bottoms,  but  now  their 
smooth  slopes  come  to  an  end  in  terraces  and  are  constantly  interrupted  by  small  valleys 
and  gullies  of  recent  origin.  These  valleys  may  be  just  wide  enough  for  a  small  torrential 
stream,  or  several  miles  wide.  Their  depth  may  be  a  few  feet  or  hundreds.  Their  sides 


*  Cam.  Inst.  Wash.  Pub.  99,  1908. 


20 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


may  show  an  unbroken  slope,  gentle  or  steep  as  the  case  may  be,  or  may  be  broken  into 
four  or  five  terraces.  Practically  every  waterway,  large  or  small,  is  bordered  by  one  or 
more  terraces.  They  form  the  third  of  the  persistent  elements  of  the  landscape.  Not  so 
noticeable  as  the  rough  mountains,  not  furnishing  a  home  and  land  for  tillage  to  the  ancient 
inhabitants  like  the  bahadas,  they  are  in  some  ways  quite  as  important.  Their  interpreta¬ 
tion,  unlike  that  of  the  other  features,  is  by  no  means  a  matter  of  general  agreement. 
Therefore,  when  we  have  briefly  discussed  the  vegetation  of  the  country,  I  shall  devote  a 
chapter  to  a  consideration  of  the  two  opposing  theories,  climatic  and  tectonic,  which  have 
been  advanced  in  explanation  of  the  terraces. 


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A.  Alluvial  deposits  burying  the  bottoms  of  mesquite  trees  on  the  lower  Santa  Cruz  near  Charco  Yuma. 

B.  Typical  vegetation  of  Southern  Arizona,  giant  cactus,  Cholla,  mesquite  bushes,  grease- wood.  etc. 

C.  Alluvia!  terraces  and  typical  vegetation  of  a  river  valley  in  Northern  Sonora. 


CHAPTER  III. 

THE  ARBOREAL  VEGETATION  OF  THE  MONSOON  DESERT. 

A  detailed  description  of  the  vegetation  of  Arizona  and  New  Mexico  would  be  out  of 
place  in  the  present  volume.  Not  only  does  it  lie  beyond  the  writer’s  field  of  knowledge, 
but  it  has  been  ably  done  in  MacDougal’s  volume  on  the  Deserts  of  North  America,*  and 
in  other  publications  of  the  Desert  Laboratory.  The  purpose  of  this  chapter  is  merely  to 
call  attention  to  one  of  the  pecuhar  results  of  the  twofold  rainy  season  of  the  southwest. 
The  result  is  much  more  obvious  in  the  warm  southern  parts  of  Arizona  than  in  the  regions 
of  greater  altitude.  Hence  I  shall  confine  myself  chiefly  to  that  region. 

To  one  familiar  with  the  deserts  of  the  Eastern  Hemisphere  or  of  other  parts  of  North 
America,  the  vegetation  of  the  less  elevated  portions  of  southern  Arizona,  northern  Sonora, 
and,  to  a  less  extent,  southern  New  Mexico  is  surprising.  The  annual  rainfall  at  Tucson 
at  an  elevation  of  2,300  feet  amounts,  it  will  be  remembered,  to  about  12  inches.  The 
amount  elsewhere  may  be  seen  by  referring  to  figure  1  on  page  10.  Few  parts  of  southern 
Arizona  and  New  Mexico  have  more  than  12  inches  of  rain,  most  of  the  country  has  less, 
and  Yuma,  as  is  well  known,  has  only  about  3  inches.  So  far  as  habitability  is  concerned 
the  country  is  genuinely  a  desert.  There  are  several  places  in  Arizona,  especially  in  the 
southwestern  part  of  the  State,  where  the  whole  of  Massachusetts  with  its  3,500,000 
people  could  be  set  down  without  disturbing  a  single  farm,  or  cattle  ranch,  or  any  other 
place  where  people  are  making  a  hving  from  the  soil  as  distinguished  from  mines  and 
railroad  enterprises;  the  same  is  true  of  Sonora.  Nevertheless  the  general  aspect  of  the 
country  is  green,  even  in  the  dry  seasons.  Most  regions  having  a  rainfall  of  only  10  or  12 
inches  are  bare  and  treeless,  as  may  be  seen  in  Utah  or  Nevada,  or  in  Syria  and  Persia. 
There  arboreal  vegetation,  away  from  the  water-courses,  is  almost  entirely  restricted  to 
insignificant  grayish-green  forms  like  sage-brush.  In  a  measure  this  is  due  to  unrestricted 
grazing,  but  by  no  means  entirely;  for  in  places  where  flocks  never  graze  the  bushes  are 
small  and  rare  and  trees  are  unknown.  In  the  southern  part  of  Arizona,  on  the  contrary, 
bushes  are  found  almost  everywhere  except  on  the  mountain  sides,  and  the  aspect  of  the 
desert  is  distinctly  arboreal  and  verdant.  Thousands  of  square  miles  are  covered  with  the 
useless  creosote  bush,  a  shrub  which  grows  to  a  height  of  from  4  to  6  feet  or  more,  and  is 
thickly  studded  with  small  gummy  leaves.  The  individual  bushes  are  commonly  10  or  15 
feet  apart,  and  the  ground  between  them  is  often  bare  or  covered  only  with  a  short-lived 
growth  of  grass.  Nevertheless,  the  bushes  are  close  enough  to  one  another  to  give  a  pro¬ 
nounced  green  color  to  the  landscape  as  a  whole.  In  addition  to  the  creosote  bush  there 
are  numerous  larger  species  of  bushes  and  trees.  The  most  prominent  is  the  mesquite, 
which  sometimes  grows  to  a  height  of  40  or  50  feet  in  relatively  damp  bottom  lands.  Com¬ 
monly  it  attains  a  height  of  15  or  20  feet,  and  grows  in  loose  groves  resembling  extensive 
peach  orchards.  Among  the  creosote  bushes  and  mesquites  numerous  other  trees  are 
found,  such  as  the  ironwood  and  several  other  species  of  acacia,  and  the  palo  verde,  whose 
green  bark,  tiny  round  leaves,  and  dainty  yellow  blossoms  constantly  attract  attention. 
Everywhere,  too,  a  profusion  of  healthy  green  cacti  add  to  the  verdure,  some  being  re¬ 
cumbent,  hke  the  smaller  forms  of  the  flat-leaved  prickly  pear,  some  bushy  like  the  spiny, 
many-branched  cholla,  and  some  assuming  the  dimensions  of  large  trees,  like  the  saguaro 
or  giant  cactus,  whose  fluted  columns  are  often  40  or  50  feet  high.  (See  Plate  1,  p.  34.) 


*  D.  T.  MacDougal:  Botanical  Features  of  North  American  Deserts.  Cam.  Inst.  Wash.  Pub.  99,  1908. 

21 


22 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


The  peculiarly  verdant  arboreal  character  of  the  desert  of  southern  Arizona  and  Sonora 
appears  to  be  due  primarily  to  the  double  rainy  period.  In  the  majority  of  deserts  rain 
falls  only  during  a  single  season,  which  is  often  the  winter,  when  the  temperature  is  un¬ 
favorable  to  growth.  Inasmuch  as  the  winters  of  the  less  elevated  portions  of  Arizona  do 
not  last  long,  those  portions  are  favored  with  a  relatively  good  growth  of  herbaceous 
annuals  in  winter,  and  also  in  summer,  as  is  fully  described  in  the  paper  of  MacDougal 
previously  referred  to.  Trees,  as  is  well  known,  require  a  prolonged  season  of  growth.  The 
rains  of  the  brief  moist  season  in  most  deserts  do  not  store  the  ground  with  sufficient 
moisture  to  enable  the  trees  to  mature  their  various  organs  and  produce  seed.  In  the 
region  under  discussion,  however,  the  winter  rains  start  the  growth  of  trees,  and  supply 
sufficient  moisture  to  enable  the  plants  to  subsist  until  the  arrival  of  the  summer  rains. 
These  lengthen  the  growing  season  to  a  period  equal  to  that  in  many  regions  which  are  much 
better  watered.  Of  course,  moisture  is  scarce  for  a  long  interval  during  the  rainless  fore¬ 
summer,  and  the  ground  is  too  dry  for  ordinary  trees.  Nevertheless,  many  desert  species 
have  become  adapted  to  the  double  rainy  season.  Hence,  although  Arizona  is  a  genuine 
desert  from  an  agricultural  point  of  view,  the  scenery  of  the  southern  part  by  no  means 
suggests  this.  The  country  is  far  more  verdant  than  many  regions  whose  agricultural 
possibilities  are  much  greater. 

In  the  elevated  plateau-regions  of  northern  Arizona  and  New  Mexico  the  vegetation 
is  of  the  usual  type,  chiefly  grasses,  small  quick-growing  herbs,  and  low  stunted  bushes 
of  the  sage  type.  This  is  due  to  the  relatively  small  amount  of  rain  in  summer  as  com¬ 
pared  with  winter,  and  to  the  length  of  the  winter,  which  prevents  growth  in  February, 
March,  and  even  April.  Thus  the  twofold  rainy  season  is  largely  robbed  of  its  effect.  In 
the  higher  mountains,  at  an  altitude  of  7,000  feet  or  more,  pine  forests,  fringed  with  oaks 
on  the  lower  border,  cover  large  areas.  Here  the  moisture  of  the  winter  remains  in  the 
ground  so  late  that  there  is  practically  only  one  growing  season. 


CHAPTER  IV. 

THE  CLIMATIC  THEORY  OF  TERRACES. 

The  preceding  general  description  of  the  climate  of  Arizona  and  New  Mexico,  and  of  the 
relation  of  that  climate  to  topography  and  vegetation,  prepares  the  way  for  a  consideration 
of  the  various  lines  of  evidence  which  seem  to  indicate  that  distinct  climatic  changes  have 
taken  place  in  post-glacial  times  and  even  in  the  period  covered  by  the  written  history  of 
the  eastern  hemisphere.  Among  purely  physical  phenomena,  unrelated  to  man  or  his 
work,  none  is  so  widespread  or  so  important  in  its  bearing  on  this  problem  as  the  alluvial 
terraces  described  briefly  in  the  chapter  on  topography.  Until  within  the  past  ten  years 
such  terraces,  if  they  were  discussed  at  all,  were  almost  invariably  assumed  to  be  the 
result  of  movements  of  the  earth’s  crust.  As  a  rule,  however,  they  were  dismissed  with 
a  word,  on  the  tacit  assumption  that  they  were  not  of  sufficient  importance  to  warrant 
further  discussion.  W.  D.  Johnson,  and  possibly  others,  had  recognized  that  terraces 
may  originate  from  climatic  variations,  not  only  in  glaciated,  but  in  non-glaciated  regions.* 
Nevertheless,  the  possibility  of  such  origin  in  specific  cases  was  rarely  or  never  discussed. 
The  first  papers  to  consider  the  matter  with  any  fullness  were  two  upon  Russian  Turkestan 
by  Professor  Davis  and  the  writer,  and  another  upon  Persia  also  by  the  present  writer. 
All  three  were  published  by  the  Carnegie  Institution  in  1905  in  a  volume  entitled  “Explora¬ 
tions  in  Turkestan.”  Since  then  the  subject  has  received  some  attention  in  the  writings 
of  Barrellf  and  others,  but  no  one  has  yet  definitely  attempted  to  test  the  climatic  theory  of 
terraces  by  applying  it  to  a  definite  region  in  America  and  working  out  the  agreement  or  dis¬ 
agreement  of  the  facts  with  this  theory  and  with  its  chief  rival.  Accordingly  I  shall  do  this, 
even  at  the  risk  of  repeating  some  things  which  I  have  said  elsewhere  in  regard  to  Asia. 

Terraces,  although  a  common  feature  of  the  landscape  in  many  arid  regions,  are  not  of 
great  importance  in  themselves.  As  possible  indicators  of  climatic  changes  in  recent  geo¬ 
logical  times,  however,  they  are  of  the  first  importance.  Geologists  have  long  been  keenly 
alive  to  the  fact  that  the  interior  of  our  planet  is  in  a  state  of  incessant  change  which 
manifests  itself  in  the  varied  phenomena  of  crustal  movements,  the  bursting  forth  of  vol¬ 
canoes,  and  the  transformation  of  rocks  by  the  development  of  new  magmas  or  by  the 
processes  of  metamorphism.  Yet,  in  regard  to  climate,  they  have  until  recently  tacitly 
assumed  that,  with  the  exception  of  a  few  unique  cases  such  as  the  Permian  and  Pleistocene 
glacial  periods,  the  conditions  of  the  earth  have  either  remained  uniform  for  ages  or  have 
been  subject  only  to  the  extremely  slow  variations  postulated  by  the  nebular  hypothesis. 
Recently,  however,  a  change  has  taken  place,  and  geologists  are  beginning  to  realize  that 
at  certain  special  epochs  the  climate  of  the  past  has  been  subject  to  great  changes.  The 
discovery  of  evidences  of  a  Cambrian  glacial  period  by  Willis  and  others,  and  of  a  pre- 
Cambrian  period  by  Coleman,  and  still  more  the  development  of  the  planetesimal  hy¬ 
pothesis  by  Moulton  and  Chamberlain,  have  introduced  a  wholly  new  conception.  Never¬ 
theless,  except  for  a  few  tentative  suggestions,  such  as  those  of  Gilbert,  Davis,  and  BarreU,J 
the  general  opinion  still  remains  that  climatic  changes  are  very  slow  in  occurrence,  that 
throughout  most  of  geologic  time  conditions  of  practical  uniformity  have  prevailed,  that 
the  changes  of  the  glacial  period  came  to  an  end  before  the  beginning  of  the  historic  period, 
and  that  since  that  time  the  climate  of  the  world  has  remained  uniform.  If  the  conclusions 

*  W.  D.  Johnson:  The  High  Plains  and  Their  Utilization.  Twenty-first  Ann.  Kept.  U.  S.  Geol.  Survey,  part  iv,  1901, 
pp.  626,  628-630. 

t  Joseph  Barrel! :  The  Relations  between  Climate  and  Terrestrial  Deposits.  Journal  of  Geology,  vol.  xvi,  1908. 
i  G.  K.  Gilbert:  Rhythms  and  Geologic  Time.  Proc.  Am.  Assn,  for  Adv.  of  Science,  vol.  49,  pp.  1-19. 

W.  M.  Davis:  Explorations  in  Turkestan.  Vol.  1,  Cam.  Inst.  Wash.  Pub.  26,  1905. 

Joseph  Barrell:  Origin  and  Significance  of  the  Mauch  Chunk  Shale.  Bull.  Geol.  Soc.  Am.,  vol.  18, 1907,  pp.  449-476. 

23 


24 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA, 


reached  in  the  following  pages  are  correct,  however,  changes  of  considerable  importance 
are  still  in  progress,  and  there  is  a  strong  possibility  that  throughout  the  course  of  the 
world’s  whole  history  climate  may  frequently  have  been  subjected  to  conditions  of  high 
variability.  It  may  have  remained  constant  for  hundreds  of  thousands  of  years,  but  on 
the  other  hand  it  may  have  changed  suddenly  at  any  time.  Only  by  an  exhaustive  study 
of  all  the  possible  evidences  of  change  can  we  reach  certainty  on  this  point,  and  only  then 
can  we  test  such  theories  as  those  of  the  relation  of  the  carbonic  acid  of  the  atmosphere  to 
glacial  periods,  the  effect  of  volcanic  dust  in  cutting  off  the  sun’s  heat,  or  the  effect  of  solar 
variations  upon  climate  and  thus  upon  the  evolution  of  life. 

TERRACES  OF  THE  TUCSON  REGION. 

Let  US  turn  now  to  our  immediate  problem,  the  origin  of  terraces.  We  will  begin 
with  a  specific  example,  taking  up  first  the  most  recent  terraces.  Near  the  city  of  Tucson 
the  Santa  Cruz  River  flows  in  a  newly  cut  channel  from  100  to  300  feet  wide  and  12  or  15 
feet  deep.  The  channel  has  been  excavated  by  the  stream  within  the  last  25  years.  Its 
edges  rise  steeply  from  the  sandy  river-bed  to  a  flat  alluvial  plain  from  half  a  mile  to  a  mile 
or  more  in  width.  The  plain  is  in  part  covered  with  a  thick  growth  of  mesquite  and  in  part 
with  irrigated  fields.  Before  the  cutting  of  the  new  channel  and  the  consequent  partial 
draining  of  the  plain,  much  of  it  was  covered  with  sacaton,  a  species  of  bunch  grass, 
5  or  6  feet  high,  which  flourishes  only  in  places  where  flood  water  occasionally  keeps  the 
ground  thoroughly  soaked  for  a  time.  The  alluvial  plain,  in  its  present  form,  can  not  be 
of  great  age  geologically  speaking,  or  even  as  measured  by  human  standards;  for  Professor 
R.  H.  Forbes,  of  the  Arizona  Experiment  Station,  has  found  pottery  in  the  banks  on  the 
borders  of  the  channel  at  a  depth  of  10  feet  below  the  plain,  and  similar  finds  have  been 
made  elsewhere.  The  pre-Columbian  inhabitants  of  America  can  scarcely  have  dug  to  a 
depth  of  10  feet,  or,  at  least,  would  scarcely  have  done  so,  without  iron  tools  of  any  sort. 
Therefore  we  infer  that  since  the  time  when  pottery  was  in  use  the  alluvial  plain  at  Tucson 
has  been  built  up  considerably.  It  scarcely  needs  the  pottery  to  prove  this,  for  when 
Americans  first  settled  here,  half  a  century  ago,  the  plain  was  flooded  with  water  every 
year,  so  that  sometimes  the  mail  had  to  be  ferried  across  a  mile  of  water.  The  floods  were 
not  so  muddy  at  that  time  as  they  now  are,  but  a  certain  amount  of  sediment  was  carried 
and  was  deposited  where  the  water  spread  out. 

The  alluvial  plain  is  bordered  by  a  gentle  terrace  of  gravel,  10  to  20  feet  high,  according 
to  its  distance  from  the  stream.  The  top  of  the  terrace  forms  part  of  the  main  bahada 
slope  on  which  is  located  the  city  of  Tucson.  At  first  sight  the  terrace  seems  to  be  far 
more  gravelly  than  the  alluvial  plain,  but  this  is  not  so  marked  a  feature  as  superficial 
conditions  would  indicate.  The  surface  of  the  plain  is  everywhere  composed  of  fine  silt, 
but  in  its  interior,  as  disclosed  by  the  cutting  of  the  river,  layers  of  gravel  are  by  no  means 
uncommon.  The  surface  of  the  bahada,  on  the  contrary,  is  almost  everywhere  gravelly,  but 
its  interior  contains  a  large  proportion  of  fine  material,  partly  in  the  form  of  ordinary  silt 
and  partly  in  the  form  of  a  calcareous  silty  formation  known  as  caliche.  The  preponderance 
of  pebbles  on  the  surface  is  largely  the  result  of  the  process  by  which  the  so-called  ‘‘desert 
pavements”  are  formed.*  In  an  arid  country  eolian  erosion  gradually  removes  the  finer 
materials  from  the  surface,  but  leaves  the  pebbles.  In  course  of  time  the  process  goes  so 
far  that  the  entire  surface  becomes  covered  with  pebbles  which  assume  the  form  of  a 
regular  pavement  and  check  further  erosion  of  the  underlying  fine  materials.  In  the 
bahada  on  which  Tucson  is  located  the  process  has  not  gone  so  far  as  to  produce  a  genuine 
pavement,  but  it  has  progressed  sufficiently  to  make  the  surface  much  more  gravelly 


*  See  Tollman,  op.  cit.  Journal  of  Geology,  vol.  xvii,  1909,  p.  149. 


THE  CLIMATIC  THEORY  OF  TERRACES. 


25 


than  the  interior,  and  to  show  that  the  bahada  is  decidedly  older  than  the  alluvial  plain 
at  the  base  of  the  terrace  which  borders  it.  The  development  of  the  calcareous  deposit 
known  as  caliche  is  also  a  sign  that  the  materials  of  the  bahada  are  older  than  those  of 
the  alluvial  plain. 

To  the  superficial  eye  it  seems  as  if  the  bahada  which  stretches  from  Tucson  south¬ 
eastward  in  a  splendid  green  slope  for  a  score  of  miles  toward  the  mountains  were  the  uni¬ 
form  product  of  a  single  period  of  deposition.  Nevertheless,  at  various  points  other 
deposits  belonging  to  higher  terraces  rise  above  it.  For  instance,  at  the  end  of  the  Speed¬ 
way  which  runs  seven  miles  eastward  from  the  city,  a  line  of  low  hills  projects  above  the 
plain.  They  are  composed  of  gravel  of  the  same  nature  as  that  of  the  surrounding  portion 
of  the  main  bahada,  but  of  somewhat  coarser  texture.  On  every  side  they  are  isolated 
from  the  mountains  by  means  of  the  plain  of  the  main  bahada;  yet  it  seems  fairly  certain 
that  they  were  originally  part  of  a  higher,  older  bahada  which  bore  the  same  relation  to 
the  one  on  which  Tucson  lies  as  that  bears  to  the  alluvial  plain,  or  as  the  alluvial  plain 
bears  to  the  foot  or  two  of  materials  which  have  been  laid  down  in  the  river  channel  since 
the  last  flood.  A  few  miles  to  the  north  of  the  hills,  that  is,  on  the  north  side  of  the  sandy 
channel  of  Rillito  Wash  at  the  base  of  the  Santa  Catalina  Mountains,  a  much  more  distinct 
portion  of  the  old  bahada  is  seen.  It  here  takes  the  form  of  a  regular  terrace  of  the  same 
form  as  the  lower  terrace  on  which  Tucson  is  built.  Above  it  rises  still  another  terrace 
whose  gently  sloping  flat  top  presents  the  unmistakable  appearance  of  a  bahada.  It  is 
composed  of  gravel,  very  coarse  here  because  of  proximity  to  the  mountains.  Evidently 
it  once  extended  unbroken  to  the  mountains  on  the  one  hand,  and  far  out  to  the  center  of 
the  valley  on  the  other.  Now  it  forms  a  flat-topped  and  almost  isolated  plateau  connected 
with  the  mountains  only  at  one  or  two  points.  At  a  still  higher  level,  traces  of  a  fourth 
terrace  and  bahada  appear,  but  are  not  sufficiently  distinct  to  allow  of  certain  identification. 

Similar  terraces  occur  along  every  stream  which  I  saw  anywhere  near  the  mountains 
during  three  months’  stay  in  the  country.  On  the  minor  tributaries  and  far  downstream 
on  the  main  drainage  lines  only  one  terrace  is  commonly  visible,  but  higher  up  the  number 
increases  along  streams  of  any  size.  In  many  cases,  similar  to  that  just  described,  only 
a  single  terrace  appears  at  first,  but  careful  examination,  even  without  going  farther 
upstream,  usually  shows  that  there  are  several.  As  a  rule  the  older  terraces  are  so  com¬ 
pletely  dissected  that  they  have  disappeared  except  in  a  few  favored  spots,  where  they  are 
preserved  either  as  stumps,  so  to  speak,  on  the  lower  flanks  of  the  mountains  high  above 
the  limits  of  the  lowest  main  terrace,  or  else  as  isolated  islands  in  the  form  of  flat-topped 
hills,  such  as  those  along  the  southwest  base  of  the  Catalina  Mountains. 

Back  in  the  mountains  toward  the  heads  of  the  main  streams  the  number  of  terraces 
is  commonly  four  or  five.  Thus  at  the  head  of  the  Canada  del  Oro,  on  the  northeast  side 
of  the  Santa  Catalina  Mountains,  Dr.  MacDougal  states  that  there  are  five  distinct  terraces. 
Lower  down  in  the  same  valley  I  saw  three,  very  perfectly  developed.  On  the  opposite 
side  of  the  same  mountains  the  three,  or  possibly  four,  main  terraces  of  the  Rillito  have 
already  been  described.  In  addition  to  these  there  is  a  minor  terrace  bordering  the  present 
flood  plain.  In  the  upper  valley  of  the  Pantano,  a  main  tributary  which  joins  the  Rillito 
from  the  south  just  before  that  waterway  unites  with  the  Santa  Cruz,  numerous  terraces 
can  be  seen  to  the  south  and  southwest  of  the  Empire  Ranch  at  the  eastern  base  of  the  high 
Santa  Rita  Mountains.  In  Gardner  Canyon,  for  instance,  the  upper  terrace  appears  as  a 
broad  bahada  lying  close  to  the  base  of  the  mountains,  while  farther  out  in  the  main  valley 
of  the  Pantano  portions  of  it  can  be  seen  as  isolated  hills  with  flat  tops;  like  all  the  rest  of 
the  terraces  it  is  composed  of  coarse  gravel  full  of  cobblestones  and  small  boulders.  The 
next  terrace  is  very  pronounced,  and  can  be  seen  over  a  wide  range  of  country.  Where  I 
climbed  it,  the  height  amounts  to  30  or  40  feet,  and  the  fairly  steep  slope  leading  up  to  the 
broad  fiat  bahada  is  covered  with  loose  boulders  and  cobbles.  The  third  is  less  pronounced 


26 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


than  the  second;  it  is  less  than  half  as  high,  and  has  a  much  more  gentle  slope.  Below  it 
there  is  a  little  terrace  only  about  5  feet  in  height,  which  scarcely  deserves  to  be  noticed. 
Next  comes  a  fifth,  which  is  the  most  pronounced  of  all;  it  corresponds  to  the  one  on  which 
the  city  of  Tucson  is  built.  Below  it  there  is  what  may  be  termed  an  incipient  sixth  terrace 
corresponding  to  the  edges  of  the  new  channel  at  Tucson. 

TERRACES  OF  OTHER  ARID  PORTIONS  OF  NORTH  AMERICA. 

Forty  or  50  miles  to  the  southwest  of  the  northward-draining  Pantano  the  main  branch 
of  the  Magdalena  River  in  Mexico  drains  to  the  south.  Here  again  terraces  are  highly 
developed,  as  may  well  be  seen  at  Cocospera  (see  Plate  1,  c,  page  34),  near  one  of  the  old 
Spanish  missions  which  are  so  picturesque  a  feature  of  all  this  region.  The  total  number 
of  terraces  here  amounts  to  seven,  in  addition  to  the  terraced  edge  of  the  present  flood-plain. 
One  of  the  seven,  however,  is  only  3  or  4  feet  high,  and  is  not  continuous,  so  that  it  scarcely 
deserves  to  be  counted.  Two  of  the  others  lie  close  together  and  usually  merge  into  one. 
All  alike  are  composed  of  gravel  and  appear  to  be  the  same  type  as  those  of  the  other 
valleys  of  the  region. 

Terraces  of  the  kind  here  described  are  not  confined  to  the  valleys  mentioned  above; 
they  occur  in  that  of  the  San  Pedro  to  the  east  of  the  Santa  Cruz  and  in  that  of  the  Gila  to 
the  north.  In  northern  Arizona  the  Grand  Wash  in  the  western  part  of  the  State  contains 
one  or  two  terraces  which  appear  to  be  of  the  same  type,  and  so  does  the  Kanab  Canyon 
in  southern  Utah,  which  I  have  elsewhere  described  in  connection  with  the  terraces  of 
Persia  and  Turkestan.*  In  the  northeastern  part  of  Utah  the  Provo  River,  which  rises  in 
the  Uinta  Mountains  and  flows  south  westward  through  the  Wasatch  Range  to  Great  Salt 
Lake  near  Provo,  traverses  a  valley  which  shows  a  fine  series  of  terraces  of  the  same  type 
prevalent  farther  south.  The  same  is  true  of  Kamas  Creek,  flowing  north  to  the  Weber 
in  the  same  region.  In  Montana  similar  phenomena  of  the  upper  Yellowstone  and  other 
valleys  may  perhaps  be  connected  with  glaciation,  but  this  can  not  be  true  of  those  already 
described  in  Arizona  nor  of  those  of  the  Rio  Grande,  Tularosa,  and  other  streams  in  New 
Mexico.  Still  other  terraces  which  can  not  be  of  glacial  origin  occur  in  various  parts  of  old 
Mexico  and  will  be  described  later.  All  these  are  only  a  part  of  the  cases  of  non-glacial 
terracing  which  the  writer  has  himself  seen. 

From  the  descriptions  of  others  it  appears  that  there  are  many  other  valleys  in  the  semi- 
arid  portions  of  America  which  are  similarly  characterized  by  terraces.  For  example, 
since  the  completion  of  the  original  manuscript  of  this  chapter  the  Journal  of  Geology  for 
October  1910,  vol.  xviii,  pp.  601-632,  has  appeared  containing  an  article  by  J.  L.  Rich, 
who  describes  terraces  of  apparently  the  same  sort  in  Wyoming.  Mr.  Rich  has  also 
presented  before  the  Association  of  American  Geographers  a  paper  in  which  he  discusses 
the  process  of  terrace-making  as  it  has  occurred  during  the  last  half  century.  In  general 
he  adopts  the  theories  of  the  present  writer  as  set  forth  in  “Explorations  in  Turkestan,” 
and  in  a  paper  on  “Some  Characteristics  of  the  Glacial  Period  in  Non-glaciated  Regions.”t 

TERRACES  OF  FOREIGN  COUNTRIES. 

Turning  to  foreign  countries,  in  the  publications  already  named,  I  have  discussed  similar 
terraces  distributed  from  Turkey  on  the  west  to  China,  3,000  or  4,000  miles  away,  on  the 
east.  In  Greece  they  occur  along  rivers  such  as  the  Alpheios,  and  appear  to  have  had  a 
share  in  the  burial  of  the  ruins  of  Olympia.  J  Apparently  some  terracing  process  has  been 
very  active  in  the  arid  or  semi-arid  mountainous  regions  of  the  world  in  the  most  recent 

*  Explorations  in  Turkestan,  Expedition  of  1903.  Cam.  Inst.  Wash.  Pub.  26,  1905,  p.  272. 

t  Bulletin  of  the  Geological  Society  of  America,  vol.  18,  pp.  351-388. 

t  The  Burial  of  Olympia,  by  Ellsworth  Huntington.  Geographical  Journal,  London,  vol.  36,  1910,  pp.  657-686. 


THE  CLIMATIC  THEORY  OF  TERRACES. 


27 


geological  times,  and  the  activity  seems  to  have  persisted  down  almost  to  the  present  day, 
or  even  to  be  still  in  operation.  Clearly  the  truth  can  not  be  ascertained  without  a  realiza¬ 
tion  of  the  fact  that  the  phenomena  are  widespread.  It  is  scarcely  going  too  far  to  say  that 
in  the  dry,  non-glaciated  portions  of  North  America  and  Eurasia  regions  containing  high 
mountains  of  unsubdued  topography  are  usually  characterized  by  a  peculiar  type  of  terraces 
which  bear  so  close  a  resemblance  to  one  another  that  they  all  appear  to  be  due  to  a  single 
cause.  Hence  the  terraces  are  of  great  importance  because  they  represent  one  of  the  latest 
and  most  widespread  of  geological  processes.  In  attempting  to  explain  them  it  must  con¬ 
stantly  be  borne  in  mind  that  we  are  dealing  with  a  phenomenon  which  is  as  widespread 
as  glaciation,  but  which  has  taken  place  in  non-glaciated,  arid  regions  during  the  same 
period  of  time  which  has  seen  the  intermittent  advance  and  retreat  of  the  ice-sheet  from 
the  moist  lands  of  the  north. 

THE  STRUCTURE  OF  THE  TERRACES. 

Before  proceeding  to  discuss  the  two  theories  of  tectonic  and  climatic  origin  of  terraces, 
let  us  first  consider  the  general  structure  of  the  terraces  themselves.  In  doing  this  the  facts 
will  be  drawn  only  from  a  fimited  area  in  southern  Arizona  and  northern  Mexico,  but  the 
general  statements  apply  with  equal  truth  to  other  parts  of  North  America  and  to  Asia. 
The  upper  portions  of  the  terraces  universally  consist  of  alluvial  material  varying  in  texture 
from  coarse  cobbles  and  boulders  to  fine  silt,  according  to  the  distance  from  the  mountains. 
In  the  majority  of  cases  the  entire  terrace  is  alluvial  from  top  to  bottom,  although  the 


Fig.  5. — Cross-section  illustrating  the  Formation  of  Climatic  Terraces. 

different  layers  may  vary  greatly  in  texture,  a  part,  for  instance,  being  composed  of  coarse 
gravel,  while  an  underlying  layer  consists  of  fine  clay.  In  many  cases,  however,  solid 
rock  crops  out  below  the  alluvial  material.  In  such  cases  it  is  clear  that  the  gravel  which 
lies  on  the  rock  and  forms  an  upper  terrace,  and  that  which  lies  against  it  at  its  base  and 
forms  a  lower  terrace,  are  not  of  the  same  age.  This  can  be  plainly  seen  on  the  right  of  figure 
5,  where  the  deposition  of  the  gravel  of  terrace  A  was  clearly  separated  from  that  of  C  by  a 
period  of  erosion,  or  in  fact  by  two  periods  of  erosion  in  this  particular  case.  In  other  cases, 
such  as  that  already  described  at  Tucson,  a  lower  terrace  may  consist  of  fine  silt,  while 
the  one  just  above  it  is  composed  of  gravel.  Here  again  a  period  of  erosion  must  have 
intervened,  as  is  illustrated  on  the  left  of  figure  5,  for  otherwise  it  would  not  be  possible 
to  have  an  unconformity  such  as  that  which  exists  between  the  coarser  deposits  of  B  and  the 
finer  ones  of  C.  In  still  other  cases  the  deposits  of  two  contiguous  terraces,  such  as  A  and 
B,  are  so  similar  that  it  is  not  possible  to  ascertain  whether  they  were  separated  by  a  period 
of  erosion  or  whether  they  are  parts  of  a  single  deposit  which  was  first  laid  down  in  suffi¬ 
cient  depth  to  reach  the  level  A,  and  was  then  in  part  eroded  to  the  level  B.  Terraces  of 
all  kinds,  or  combinations  of  the  various  types,  may  be  found  together,  and  a  single 
terrace  may  pass  from  one  type  to  another,  as  it  is  followed  up  or  down  stream. 


28 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


All  the  terraces  point  to  a  single  series  of  events.  They  indicate  that,  on  a  small  scale, 
the  streams  have  repeatedly  passed  through  what  may  well  be  called  cycles.  Let  us  assume 
that  a  cycle  begins  at  a  time  when  the  streams  are  engaged  in  deepening  and  widening  their 
channels,  and  let  us  suppose  that  the  process  has  gone  so  far  that  the  rivers  are  cutting  into 
bed  rock  more  or  less  rapidly.  The  next  step,  no  matter  what  our  theory  may  be,  is  a 
change  which  causes  deposition.  This  proceeds  until  the  valley  has  been  filled  to  an 
appreciable  depth  with  alluvial  deposits  which  naturally  vary  in  texture  from  time  to  time 
and  place  to  place.  Next  there  ensues  another  change  which  reverses  the  process.  It 
compels  the  streams  to  deepen  their  channels  at  first  and  then  to  widen  them.  Constant 
repetition  of  these  two  processes  on  an  ever-diminishing  scale  has  produced  the  terraces 
which  are  now  so  common.  Sometimes  the  streams  have  shifted  far  to  one  side  of  the  valley 
or  to  the  other,  and  have  completely  undermined  the  older  terraces,  which  in  many  cases 
have  entirely  disappeared  or  have  been  reduced  to  mere  fragments.  In  almost  every 
main  valley,  however,  some  trace  of  older  terraces  can  be  found  by  careful  search,  and  in 
all  valleys,  large  and  small,  the  younger  ones  are  visible,  provided  the  region  is  sufficiently 
arid  and  mountainous. 

NATURE  AND  DISTRIBUTION  OF  TERRACES  ACCORDING  TO  THE  TECTONIC  HYPOTHESIS. 

We  are  now  prepared  to  test  the  two  chief  theories  of  the  origin  of  terraces  in  arid  regions. 
As  has  been  said,  neither  theory  has  yet  been  carried  to  its  logical  consequences  and  ade¬ 
quately  tested  in  reference  to  America.  In  respect,  however,  to  the  Gila  conglomerates, 
which  are  the  gravels  of  the  terraces  along  the  Gila  River,  Lee*  has  advocated  the  theory 
of  tectonic  origin,  basing  his  conclusions  on  personal  observation,  while  Barrell,t  on  the 
basis  of  wide  reading  and  most  careful  reasoning,  has  come  to  the  conclusion  that  they  are 
of  climatic  origin. 

Let  us  take  up  the  tectonic  theory  first,  and  see  exactly  what  type  of  movements  of 
the  earth’s  crust  would  be  required  to  produce  terraces  such  as  those  which  we  find  all  over 
the  Southwest.  The  primary  process  in  the  formation  of  terraces  may  be  considered  as 
deposition.  After  the  valleys  have  reached  a  certain  topographic  stage,  which  may  be 
roughly  defined  as  mature,  there  must  ensue  some  change  which  causes  erosion  to  give 
place  to  deposition.  The  amount  of  deposition  may  vary  from  tens  to  hundreds  of  feet, 
but  this  is  immaterial.  Finally,  it  must  come  to  an  end,  and  must  be  succeeded  by  erosion, 
thus  giving  rise  to  terraces.  The  problem  before  us  is  simply  this:  would  it  be  possible 
for  repeated  movements  of  the  earth’s  crust  to  give  rise  to  the  succession  of  terraces  which 
we  find  so  frequently  in  widely  separated  regions?  Alternate  periods  of  uplift  and  quies¬ 
cence  undoubtedly  cause  terraces,  such  as  those  of  the  gorge  of  the  Rhine,  but  do  they 
give  rise  to  innumerable  terraces  which  not  only  occur  in  valleys  of  every  tjq^e,  but  are  often 
composed  entirely  of  gravel  without  a  trace  of  solid  rock  throughout  their  entire  extent? 

Let  us  follow  out  the  process  of  terrace-making  by  earth  movements,  and  see  what 
results  are  obtained  under  specific  circumstances.  For  the  sake  of  simplifying  the  problem, 
let  us  assume  that  the  streams  of  a  region  are  engaged  in  broadening  and  slightly  deepening 
their  valleys.  Let  us  further  suppose  that  the  processes  of  weathering  and  erosion  have  pro¬ 
ceeded  so  far  that  the  main  streams  have  flood-plains,  although  the  minor  ones  have  none. 
In  such  a  case,  the  first  step  toward  terracing,  according  to  the  ordinary  form  of  the  tec¬ 
tonic  hypothesis,  would  be  either  an  uplift  of  the  mountains  at  the  heads  of  the  streams 
in  such  a  way  as  to  cause  excessive  erosion  with  consequent  deposition  farther  downstream, 
or  else  a  tilting  of  certain  portions  of  the  beds  of  the  streams  in  such  fashion  as  to  lessen 
the  grade  and  thereby  induce  deposition.  Other  possibilities,  such  as  the  capture  or 

*  W.  T.  Lee:  Underground  Waters  of  Salt  River  Valley,  Arizona.  Water  Supply  and  Irrigation  Paper  No.  136,  U.  S. 

Geol.  Survey,  p.  115. 

t  Joseph  Barrel! :  Relations  between  Climate  and  Terrestrial  Deposits.  Journal  of  Geology,  vol.  xvi,  1908,  pp. 

173-176. 


THE  CLIMATIC  THEORY  OF  TERRACES. 


29 


beheading  of  streams,  may  be  suggested,  but  these  are  more  or  less  accidental  occurrences 
and  can  not  influence  all  the  streams  of  a  region  in  the  same  way.  It  must  be  borne  in 
mind  that  in  99  out  of  100  of  the  terraces  which  we  are  trying  to  explain  the  flrst  process 
is  the  deposition  of  a  considerable  thickness  of  alluvium,  generally  of  a  gravelly  nature. 
We  may  therefore  disregard  all  possibilities  except  the  two  just  mentioned,  which  seem 
to  be  the  only  ways  in  which  earth  movements  can  give  rise  to  abundant  deposition  in 
the  inamediate  valleys  of  the  streams. 

To  take  the  first  possibility,  we  find  that  an  uplift  of  the  mountains  would  satisfy  the 
requirements  imposed  by  the  terraces  of  Arizona  and  elsewhere  in  one  important  respect. 
It  would  steepen  the  grade  of  the  upper  parts  of  the  streams  and  thus  increase  the  amount 
of  erosion.  This  in  turn  would  overload  the  streams  in  their  unsteepened  portions,  and 
would  cause  deposition  at  the  immediate  base  of  the  mountains,  which  is  the  place  where 
the  heaviest  deposits  actually  occur  in  the  regions  under  discussion.  The  deposits,  how¬ 
ever,  are  not  confined  to  the  base  of  the  mountains  as  they  ought  to  be  according  to  our 
present  supposition.  In  regions  of  mountainous  uplift  the  main  valleys  within  the  dis¬ 
turbed  area  are  preeminently  the  scene  of  active  erosion,  as  may  be  seen  in  the  case  of 
the  Colorado  Canyon  or  the  gorge  of  the  Rhine.  Such  valleys  ought  to  be  free  from 
accumulations  of  gravel;  yet  we  find  that  the  upper  Santa  Cruz  and  Magdalena,  for 
example,  which  according  to  the  theory  of  mountain  uplift  should  have  been  steepened  and 
caused  to  cut  gorges,  are  actually  burdened  with  enormous  deposits  of  gravel  which  con¬ 
tinue  far  back  into  the  interior  of  the  mountains.  The  same  conditions  seem  to  prevail 
in  all  regions  where  terraces  of  the  kind  here  described  are  found. 

It  is  possible  to  obviate  the  difiiculty  just  suggested  by  assuming  that  the  mountainous 
region  has  not  been  uplifted  as  a  whole,  but  that  individual  ridges  have  been  uplifted,  while 
the  intervening  main  valleys  have  remained  unaffected.  This  would  certainly  explain  the 
occurrence  of  the  gravel  in  the  main  valleys.  It  would  not,  however,  explain  the  occurrence 
of  similar  gravel  deposits  in  practically  every  one  of  the  side  valleys,  such  as  the  upper  part 
of  the  Canada  del  Oro  north  of  the  Santa  Catahna  Range  and  directly  among  the  supposedly 
uplifted  mountains.  It  would  also  involve  an  assumption  contrary  to  some  of  the  chief  con¬ 
clusions  of  geology  as  to  the  nature  of  crustal  movements.  It  would  be  necessary  to  assume 
in  the  first  place  that  important  changes  in  the  relative  attitude  of  the  neighboring  parts  of 
the  earth’s  surface  have  taken  place  in  the  very  latest  geological  times  without  leaving  any 
visible  sign  of  movement,  such  as  fault  scarps  or  gorges  due  to  uplift.  It  would  also  involve 
the  assumption  that  movements  of  the  interior  of  the  earth’s  crust  take  place  in  such  a  way 
that  all  the  ridges  and  elevated  parts  of  scores  of  mountain  systems  have  been  raised  so  as  to 
steepen  the  grade  of  the  minor  tributaries,  while  the  main  valleys  remain  unchanged.  In 
other  words,  the  assumption  is  that  the  internal  movements  of  the  earth  adjust  them¬ 
selves  most  delicately  to  the  minor  features  of  the  surface,  an  assumption  the  exact  reverse 
of  the  truth. 

There  is  another  objection  to  the  theory  that  the  terraces  are  due  to  the  intermittent 
uplift  of  the  mountains  and  the  consequent  alternation  of  periods  of  rapid  and  slow  erosion. 
The  uphft  would,  of  course,  occasion  active  deposition  at  the  base  of  the  mountains,  while 
active  erosion  was  in  progress  higher  up.  The  cessation  of  uplift  and  hence  of  active  ero¬ 
sion  among  the  mountains  would  leave  the  streams  with  comparatively  light  loads  and  thus 
cause  erosion  to  begin  in  the  piedmont  region  of  previous  deposition.  This  would  doubtless 
give  rise  to  terraces  resembUng  those  whose  origin  we  are  discussing.  Directly  among 
the  mountains,  however,  it  is  evident  that  if  erosion  were  first  active  and  then  slow,  and  if 
this  process  were  repeated  several  times,  terraces  of  rock  would  necessarily  be  formed 
at  the  same  time  that  terraces  of  gravel  were  being  foimed  lower  down.  While  erosion 
was  active  the  valleys  would  be  deepened;  when  it  became  slow  they  would  be  broadened. 
The  continual  repetition  of  these  processes  could  scarcely  fail  to  produce  a  series  of  rock 


30 


THE  CLIMATIC  FACTOE  AS  ILLUSTKATED  IN  AKID  AMEEICA. 


terraces  corresponding  to  the  gravel  terraces  lower  down,  but  exactly  the  reverse  in  phase, 
for  the  horizontal  portion  of  the  upper  terraces  would  be  synchronous  with  the  vertical 
portion  of  the  lower.  Probably  such  terraces  exist  somewhere  in  the  world.  They  are 
apparently  scarce,  however,  and  in  the  regions  under  discussion  none  has  as  yet  been 
pointed  out,  although  those  of  the  other  type  are  found  in  scores  of  valleys.  The  two 
kinds  are  scarcely  associated  in  any  such  way  as  they  would  be  if  the  ordinary  terraces 
w’ere  due  to  uplift  of  portions  of  the  earth’s  crust.  It  seems  reasonably  certain  that,  so 
far  as  most  of  the  terraces  of  arid  regions  are  concerned,  we  must  give  up  the  theory  that 
they  are  due  to  intermittent  uphft  of  the  mountains,  for  this  not  only  would  involve  an 
incredible  degree  of  agreement  between  lines  of  drainage  and  lines  of  earth  movement,  but 
also  would  demand  that  terraces  of  rock  should  be  a  characteristic  feature  of  scores  of  valleys 
where  none  are  to  be  found. 

If  uplift  of  the  mountains  is  incapable  of  explaining  the  terraces,  can  they  be  explained 
as  the  result  of  crustal  movements  which  would  diminish  the  grade  of  the  lower  portions 
of  the  streams?  The  first  step,  according  to  this  form  of  the  hypothesis,  would  be  a  tilting 
of  the  surface  of  the  earth  in  such  fashion  as  to  lessen  the  grade  of  the  rivers  and  thereby 
cause  them  to  deposit  part  of  the  load  of  detritus  which  they  were  bringing  from  the 
mountains.  The  process  of  deposition  would  continue  until  the  streams  had  filled  up  the 
low  parts  of  their  valleys  to  the  point  where  conditions  of  perfect  grade  were  obtained, 
that  is,  conditions  of  perfect  adjustment  of  load  to  velocity  and  volume.  If  the  process 
of  deposition  were  sufficiently  rapid  it  would  keep  pace  with  the  tilting,  and  would  come 
to  an  end  as  soon  as  the  tilting  ceased.  In  that  case  the  cessation  of  tilting  would  cause 
an  immediate  change  in  the  mode  of  activity  of  the  streams.  They  would  cease  to  deposit 
their  loads  in  large  quantities  and  would  tend  once  more  to  cut  down  their  channels. 
Thus  terraces  would  be  formed  which  would  possess  the  character  of  those  which  we  are 
attempting  to  explain.  Further  tilting  would  cause  renewed  deposition,  and  cessation  of 
tilting  would  permit  the  cutting  of  a  second  terrace  along  each  stream.  If  the  deposits 
due  to  the  second  tilting  did  not  reach  the  level  of  the  first  deposits,  the  first  terrace  would 
persist  with  no  changes  except  those  arising  from  ordinary  weathering  and  erosion.  Further 
repetition  of  the  tilting  process  would  of  course  cause  further  terraces,  provided  always 
that  the  later  deposits  did  not  cover  the  earlier,  and  that  the  times  of  erosion  were  not  so 
prolonged  as  to  cause  the  complete  removal  of  the  older  deposits. 

At  the  very  outset  this  form  of  the  hypothesis  of  crustal  movements  is  confronted  with 
the  same  difficulty  as  the  other  form.  The  terraces  are  in  one  sense  universal  in  arid 
regions,  but  in  another  sense  they  are  very  local.  As  has  already  been  said,  they  are  limited 
to  the  mountainous  regions,  and  more  specifically  to  those  mountainous  regions  where  the 
topography  is  still  rugged  and  the  elevation  considerable.  The  terraces  vary  in  size  in 
proportion  to  the  height  and  steepness  of  the  slopes  immediately  adjacent.  They  grow 
higher  where  the  valleys  become  narrow,  as  a  rule,  and  lower  where  the  valleys  broaden. 
Sometimes,  however,  if  the  narrow  parts  of  the  valley  happen  to  be  so  located  that  they 
have  a  steep  grade  and  are  not  plentifully  supplied  with  rock  waste  from  tributaries,  the 
case  is  reversed.  Often  the  terraces  die  out  entirely  in  the  gorges  because  the  grade  is 
such  that  no  deposition  took  place  even  in  times  of  the  heaviest  load,  or  else  because  the 
small  size  of  the  valley  has  allowed  all  the  deposits  to  be  washed  out  since  the  last  main 
epoch  of  deposition.  From  what  has  just  been  said  it  is  clear  that  the  terraces  may  be  a 
widespread  phenomenon  in  one  sense,  but  in  another  they  are  very  local,  for  their  size  and 
character  depend  largely  upon  the  condition  of  the  mountains  in  the  immediate  vicinity. 
This  means  that  the  cause,  whatever  it  may  be,  acts  upon  each  individual  river  and  mountain 
independently.  In  other  words,  general,  regional  warping  of  the  earth’s  crust  can  not  be 
appealed  to  in  explanation  of  the  phenomena.  Such  warping  would  cause  the  streams  to 
be  terraced  continuously  throughout  the  whole  district  which  was  warped,  but  would  not 


THE  CLIMATIC  THEORY  OF  TERRACES. 


31 


cause  the  terraces  to  increase  or  diminish  in  size,  and  even  to  appear  and  disappear  in 
accordance  with  purely  local  conditions  of  topography.  Moreover,  regional  warping  would 
cause  some  streams  to  be  accelerated  and  others  to  be  retarded,  according  as  they  flowed 
with  or  against  the  direction  of  warping.  Therefore  its  effect  would  be  divided  into  two 
classes.  In  the  case  of  streams  which  were  retarded  we  should  have  the  kind  of  terraces 
discussed  in  the  preceding  paragraph.  In  the  many  cases  where  the  streams  were  accel¬ 
erated,  however,  we  should  expect  to  And  young  gorges  with  terraces  of  rock  along  their 
sides.  These,  as  we  have  already  seen,  are  not  found.  If  regional  warping  is  the  cause  of 
the  terraces,  a  given  stream  ought  to  behave  differently  according  to  the  direction  in  which 
it  flows.  The  Santa  Cruz  River  heads  in  the  southern  part  of  the  State  of  Arizona.  It  first 
flows  south  for  about  20  miles  into  Mexico,  then  west  around  the  end  of  the  Santa  Rita 
Mountains,  next  north  for  60  miles,  and  Anally  northwest.  Terraces  of  the  same  type 
continue  from  the  head  clear  to  the  beginning  of  the  northwesterly  section,  where  they 
Anally  die  out.  If  any  general  warping  of  the  crust  had  taken  place,  parts  of  the  Santa 
Cruz  would  have  been  accelerated  and  parts  retarded.  Therefore  we  should  have  portions 
of  the  river  valley  assuming  the  form  of  gorges  with  rock  terraces,  and  other  portions  where 
deposition  had  taken  place  and  gravel  terraces  had  been  formed;  and  the  location  of  these 
two  types  would  have  nothing  to  do  with  the  topography  of  the  country  in  the  immediate 
vicinity.  No  such  condition  exists,  however,  and  we  seem  to  be  forced  to  abandon  the 
theory  of  general  warping  or  tilting,  whereby  the  streams  were  checked  and  forced  to  form 
deposits  and  terraces. 

In  view  of  the  preceding  paragraphs  we  are  led  to  conclude  that,  if  the  terraces  are  due 
to  a  checking  of  the  streams  by  tilting,  the  tilting  must  have  been  extremely  local  in  char¬ 
acter,  so  that  each  stream  or  portion  of  a  stream  was  affected  individually.  Here  again  we 
meet  difficulties.  If  some  parts  of  a  region  were  tilted  so  as  to  retard  certain  streams,  it 
is  inconceivable  that  other  parts  should  not  have  been  tilted  so  as  to  accelerate  the  streams, 
but  of  this,  as  has  been  so  often  said,  we  And  no  evidence.  Apparently  we  must  give  up 
the  theory  of  crustal  movements,  except  as  a  reserve  hypothesis  to  explain  exceptional 
phenomena,  or  else  we  must  conclude  that  the  interior  forces  of  the  earth  adapt  themselves 
with  the  most  minute  precision  to  the  minor  topographic  features  of  the  surface,  and  always 
act  in  such  a  way  as  to  produce  the  same  results  upon  regions  of  similar  topography. 

NATURE  AND  DISTRIBUTION  OF  TERRACES  ACCORDING  TO  THE  CLIMATIC  HYPOTHESIS. 

Turning  now  to  the  chmatic  theory  of  the  origin  of  terraces,  we  find  that  it  seems  to  fit 
all  the  conditions.  Let  us  take  up  the  matter  first  from  a  purely  theoretical  standpoint. 
For  the  sake  of  convenience,  let  us  assume  the  same  initial  conditions  as  in  the  preceding 
discussion,  namely,  that  the  streams  are  engaged  in  broadening  and  slightly  deepening  their 
valleys.  The  main  streams  are  supposed  to  have  reached  a  stage  of  development  where 
they  have  formed  flood-plains,  while  the  minor  streams  are  without  flood-plains  and  the 
topography  is  rugged.  Let  us  assume  also  that  the  climate  is  relatively  moist.  Under 
such  circumstances  the  slopes  of  the  mountains  will  be  well  covered  with  forests  and  with 
other  vegetation;  the  streams  will  be  numerous,  and  will  be  of  fairly  constant  volume  with¬ 
out  being  subject  either  to  excessive  floods  or  absolute  drying  up,  and  most  of  them  will 
discharge  into  the  main  rivers,  so  that  much  of  the  sediment  which  they  carry  will  reach 
the  sea  with  comparative  rapidity.  In  the  absence  of  any  positive  knowledge  as  to  the 
climate  of  Arizona  during  the  glacial  period,  we  can  not  say  positively  that  exactly  these 
conditions  ever  prevailed  there,  but  there  can  be  little  doubt  that  such  was  the  case,  for 
similar  conditions  still  prevail  among  the  high  mountains. 

If  moist  conditions,  such  as  have  just  been  described,  give  place  to  aridity,  many 
other  changes  will  take  place.  The  forests  and  a  large  part  of  the  other  vegetation  will  die; 
the  streams  will  diminish  in  volume,  many  will  dry  up  entirely  part  of  the  time,  and  will 


32 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


fail  to  reach  the  main  rivers  except  in  occasional  floods.  The  death  of  the  vegetation  will 
lead  to  the  denudation  of  the  mountains,  as  may  be  seen  on  a  small  scale  in  certain  places 
in  Oregon  or  the  Southern  States  where  forests  have  been  cut  and  afterward  the  ground 
has  been  burned  over  in  such  a  way  as  to  kill  off  the  roots  and  new  shoots,  or  where  land 
has  been  carelessly  plowed  in  such  fashion  that  the  rains  have  had  a  chance  to  wash  away 
the  soil.  In  a  country  where  the  climate  has  become  so  dry  that  plants  will  no  longer 
grow  in  abundance,  there  is  nothing  to  check  the  process  of  denudation,  and  ultimately 
the  slopes  will  become  almost  absolutely  naked,  as  they  are  in  Persia.  Such  a  condition 
of  extreme  denudation,  as  has  been  shown  in  one  of  the  earlier  sections  of  this  report,  is 
also  characteristic  of  the  lower  mountains  in  Arizona. 

The  rapid  removal  of  soil  from  the  slopes  of  the  mountains  will  inevitably  increase  the 
load  of  the  streams,  and  in  many  cases  will  overload  them.  Accordingly,  wherever  the 
grade  is  less  steep  than  on  the  slopes  or  in  the  minor  tributaries,  the  advent  of  aridity  will 
cause  deposition  to  begin  at  once,  either  at  the  base  of  the  mountains  or  in  the  larger 
valleys.  The  streams  which  fail  to  reach  the  main  rivers,  as  the  majority  of  those  of 
Arizona  now  do,  must  inevitably  deposit  all  the  rock  waste  which  they  carry.  Formerly 
they  bore  part  of  it  to  the  sea,  but  now  none  whatever  gets  there  in  many  cases,  and  only 
a  small  fraction  of  the  former  amount  in  the  case  of  streams  which  occasionally  run  through 
to  the  main  rivers  in  times  of  flood.  This  process  of  deposition  tends  to  build  up  deep 
accumulations  of  gravel  in  the  valley  bottoms  and  vast  fans  or  alluvial  aprons  (bahadas) 
at  the  base  of  the  mountains.  As  these  deposits  increase  in  size  the  streams  are  less  and 
less  able  to  reach  the  sea.  They  are  obliged  to  flow  for  long  distances  over  porous  deposits 
of  gravel  and  silt  which  are  rarely  saturated  with  water  and  which  accordingly  act  as  great 
sponges.  The  grade  is  continually  diminished,  also,  which  tends  to  make  the  streams 
spread  more  widely  and  therefore  evaporate  or  sink  into  the  ground  more  rapidly.  Thus, 
so  long  as  aridity  continues,  the  main  mountain  valleys  and  the  piedmont  regions  tend  to 
retain  all  the  material  which  comes  down  from  the  mountains.  Where  the  mountains  are 
high  and  the  slopes  steep  the  process  of  bringing  material  from  them  is  naturally  rapid. 

To  complete  the  process  of  terracing  the  only  requisite  is  a  return  to  moist  conditions. 
Vegetation  will  increase  in  amount,  the  streams  will  become  more  uniform  in  size  from 
season  to  season,  the  gravel  deposits  will  become  saturated  with  moisture,  the  water  of 
the  streams  will  be  less  subject  to  loss  by  sinking  into  the  ground  and  by  evaporation, 
and  the  streams  will  become  longer.  Many  streams  which  formerly  came  to  an  end  at 
the  foot  of  the  mountains  will  now  flow  through  to  the  sea.  In  their  upper  portions  they 
wall  be  supplied  with  waste  less  abundantly  than  hitherto,  because  the  greater  abundance 
of  vegetation  will  tend  to  hold  in  place  whatever  new  soil  may  be  formed.  Hence  the 
streams  will  not  be  so  heavily  loaded  with  waste  as  previously.  They  will  possess  the 
relatively  clear  character  of  rivers  in  rainy  regions,  such  as  the  Connecticut  or  the  Illinois, 
rather  than  the  muddy  character  of  the  Missouri  or  Colorado.  Being  clear,  the  rivers 
and  streams  will  also  be  ready  to  become  erosive  agents  at  the  first  opportunity.  They 
will  find  their  opportunity  when  they  leave  the  mountains  and  flow  out  beyond  the  limits 
ordinarily  reached  in  the  preceding  dry  epoch.  Figure  6  illustrates  the  matter.  Suppose 
that  originally  a  stream  flowed  from  the  mountains  at  A  down  into  the  low  country  at  C, 
and  to  the  ocean  at  JE.  During  an  ensuing  time  of  aridity,  suppose  that  the  extreme  limit 
of  floods  was  D,  and  that  usually  the  stream  entirely  disappeared  by  the  time  it  reached  C'; 
under  such  circumstances  deposits  would  accumulate  as  shown  in  the  figure  between 
the  lower  fine  passing  through  C  and  the  upper  line  passing  through  C'.  The  lower  line 
represents  the  normal  profile  of  a  stream.  It  is  concave  upward  because,  after  a  stream 
has  once  attained  the  thoroughly  graded  condition  characteristic  of  maturity,  the  slope 
steadily  decreases  from  head  to  mouth.  A  dry  epoch  will  manifestly  destroy  the  perfect 
concave  curve,  for  there  will  be  abundant  deposition,  amounting  perhaps  to  hundreds  of 


THE  CLIMATIC  THEORY  OF  TERRACES. 


33 


feet,  at  C,  while  at  D  there  will  be  none  whatever.  Therefore  the  curve  will  assume  a  new 
form.  It  will  be  concave  as  far  as  C',  but  beyond  that  it  will  become  convex.  In  other 
words,  beyond  C'  there  will  be  a  steeper  slope  than  above  it,  or  than  formerly  existed 
beyond  C.  When  the  cHmate  becomes  more  moist,  and  the  revived  stream  flows  in  full 
force  past  C'  and  D,  and  on  to  the  sea,  its  velocity  will  naturally  be  accelerated  between 
C'  and  D.  As  it  is  not  loaded  to  its  full  capacity,  it  will  inevitably  begin  to  erode  the  gravel 
and  silt  of  its  own  previous  deposits.  A  gully  will  soon  be  formed,  and  will  rapidly  work 


A 


backward  toward  B.  In  course  of  time  the  stream  will  once  more  make  its  bed  concave 
upward,  perhaps  at  the  level  C~.  Then  it  will  widen  its  channel  as  well  as  deepen  it,  and 
we  shall  have  a  flood-plain  bordered  on  either  side  by  a  terrace. 

TERRACE-MAKING  AT  THE  PRESENT  TIME. 

The  process  described  above  seems  to  be  taking  place  on  a  small  scale  at  the  present 
time,  although  man  interposes  in  a  way  which  makes  the  matter  confusing.  To-day,  as 
has  been  said,  the  Santa  Cruz  River  flows  in  a  channel  from  100  to  300  feet  wide  and  from 
10  to  20  feet  deep.  The  channel  is  cut  in  a  smooth  alluvial  plain  from  half  a  mile  to  a  mile 
wide.  Thirty  years  ago  the  alluvial  plain  was  a  genuine  flood-plain,  and  there  was  no  inner 
channel  whatever.  In  times  of  flood  the  river  wandered  over  all  parts  of  the  plain,  flowing 
very  slowly  and  not  eroding  at  all.  At  Tucson,  as  we  have  seen,  the  mail  was  sometimes 
rowed  across  half  a  mile  of  water,  although  now  the  river  passes  under  a  bridge  scarcely 
100  feet  long.  The  water  must  have  carried  sediment  when  it  left  the  mountains,  but 
by  the  time  it  reached  Tucson  it  had  spread  out  so  much  and  fallen  to  such  a  low 
velocity  that  it  had  deposited  most  of  it.  A  few  miles  farther  downstream  it  came  entirely 
to  an  end  as  a  surface  stream,  although  some  underground  water  seems  to  have  come  to  the 
surface  and  made  a  new  stream  at  a  point  farther  down  toward  the  Gila.  In  the  last  two 
decades  of  the  nineteenth  century  man  interfered  with  nature’s  plans.  For  one  thing 
he  introduced  cattle,  which  ate  the  grass,  and  which  also  made  paths.  He  also  dug  ditches 
for  irrigation  in  various  places  near  Tucson,  along  the  portions  of  the  river  corresponding 
to  C'~D  in  flgure  6.  Then,  at  the  end  of  the  eighties,  there  came  some  unusually  heavy 
rains.  The  paths  trodden  by  the  cattle,  and  still  more  the  ditches  dug  by  man,  served  as 
gathering-places  for  the  water  which  had  previously  flowed  in  a  slow  sheet  among  grasses 
and  bushes.  Being  confined  in  a  channel  the  water  gained  enormously  in  erosive  power 
and  quickly  deepened  and  broadened  its  bed.  One  of  the  first  places  where  this  happened 
was  along  an  irrigation  ditch  at  the  San  Xavier  Indian  Reservation,  9  miles  south  of  Tucson. 
Later  it  occurred  in  still  worse  form  at  the  ditch  of  Mr.  Samuel  Hughes,  about  2  miles  north 
of  Tucson.  Subsequent  floods  enlarged  the  various  channels,  which  finally  coalesced  into 
a  single  broad  channel  extending  tens  of  miles  above  and  below  Tucson.  A  record  of  the 
whole  matter  can  be  seen  in  Plate  1,  figure  a,  from  a  photograph  taken  at  the  “Point”  of 

4 


34 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  Tucson  Mountains,  near  the  railroad  station  of  Rillito,  about  17  miles  northwest  of 
Tucson.  According  to  the  botanists  the  palo  verde  trees,  Parldnsonia  torreyana,  seen  partly 
embedded  in  the  bank  of  the  channel  must  have  begun  their  growth  at  a  time  when  the  place 
where  the  bottoms  of  the  trunks  now  stand  was  the  surface  of  the  alluvial  plain.  While  the 
trees  were  getting  a  start  and  making  their  first  growth,  the  plain  must  have  remained  at 
nearly  the  same  level.  Later,  however,  it  was  built  up  about  5  feet  by  river  deposits,  as 
can  be  plainly  seen.  The  condition  of  other  trees  on  all  sides  shows  that  the  entire  flood- 
plain  was  here  being  built  up.  The  length  of  time  during  which  this  process  has  been  going 
on  may  be  judged  from  the  age  of  the  trees.  I  cut  down  the  largest  of  those  seen  in  Plate  1,  a 
(page  21),  and  counted  its  rings.  They  show  that  the  tree  began  its  growth  between  the 
years  1670  and  1680  a.d.  For  about  200  years  deposition  appears  to  have  predominated 
over  erosion,  so  that  the  plain  was  gradually  built  up  by  the  addition  of  5  feet  of  silt. 
Then  in  a  decade  or  two  the  slowly  accumulated  deposits  were  swiftly  washed  away,  not 
only  here,  but  for  20  or  30  miles  upstream.  To  turn  back  to  figure  6,  it  appears  as  if 
erosion  suddenly  began  and  a  channel  was  cut  at  several  places  in  the  vicinity  of  Tucson, 
corresponding  to  C'  in  the  diagram.  Then  it  rapidly  extended  upstream  and  still  more 
downstream,  until  a  continuous  channel  30  miles  long  and  from  2  to  15  feet  deep  was 
formed.  If  we  assume  that  this  new  channel  extended  from  F  to  F',  it  is  evident  that 
the  material  which  would  formerly  have  been  deposited  in  that  region  began  to  be  carried 
below  F',  thus  completely  changing  the  area  of  maximum  deposition.  If  the  channel 
should  lengthen  still  more  the  area  of  deposition  would  be  moved  still  farther  downstream, 
and  might  even  disappear  if  the  stream  finally  attained  such  size  as  to  flow  through 
the  region  of  bahadas  into  the  main  Gila  River  and  the  sea.  This  has  not  happened, 
however,  for  great  floods  such  as  those  of  the  late  eighties  or  of  1905  are  not  common. 
During  the  relatively  dry  years  from  1906  onward  there  has  been  a  slight  tendency  for  the 
new  channel  to  silt  up.  In  other  words,  the  area  of  chief  deposition  is  shifting  upstream 
once  more. 

Here,  on  a  small  scale,  we  have  an  example  of  the  entire  process  of  terrace-making. 
First  slow  deposition  lasting  200  years,  next  a  rapid  cutting  of  a  channel  with  a  marked 
shifting  downstream  of  the  area  of  deposition,  and  finally  a  slight  and  possibly  temporary 
resumption  of  the  process  of  deposition  in  the  old  area.  Man,  to  be  sure,  has  played 
some  part  in  the  matter,  but  he  has  simply  served  as  the  means,  so  to  speak,  of  pulling  the 
trigger  which  allowed  certain  natural  forces  to  come  into  play.  If  any  other  cause,  such  as 
protracted  heavj^  rains,  had  gathered  the  water  into  a  single  channel  or  had  increased  its 
amount  so  that  it  flowed  farther  than  hitherto  and  ran  down  the  steeper  slope  of  the  con¬ 
vexity  below  Tucson,  the  same  thing  would  have  taken  place.  Moreover,  another  vital 
point  must  be  remembered.  Man  alone  did  not  cause  the  terracing.  The  cutting  out  of 
the  inner  channel  required  a  number  of  exceptionally  severe  floods,  and  the  later  slight 
refilling  of  the  channel  demanded  a  period  of  diminished  rainfall.  Possibly  the  floods 
would  have  caused  the  cutting  of  the  channel  even  without  man’s  intervention,  and  certainly 
the  refilling  has  nothing  to  do  with  man.  It  is  significant  that  this  same  type  of  channeling 
and  refilling,  this  process  of  terrace-making  on  a  small  scale,  has  occurred  at  practically 
the  same  time,  not  only  on  scores  of  streams  in  the  arid  Southwest,  but  on  an  equally  large 
number  in  various  parts  of  Asia,  where  man’s  relation  to  nature  has  not  been  subject  to 
any  change  like  that  due  to  the  settlement  of  our  own  regions.  Therefore  it  would  seem 
that  the  process  of  terrace-making  is  now  going  on  irrespective  of  man;  it  may  be  accel¬ 
erated  or  checked  by  his  actions,  but  it  seems  to  occur  primarily  in  response  to  climatic 
variations. 

Manifestly,  in  the  case  of  the  little  terraces  now  under  consideration,  earth  movements 
have  had  nothing  to  do  with  the  matter.  We  have  seen  that  in  the  past,  also,  earth  move¬ 
ments  of  sufficient  magnitude  to  produce  the  large  terraces  of  earlier  times  apparently 


THE  CLIMATIC  THEORY  OF  TERRACES. 


35 


could  not  have  occurred  without  leaving  evidences  in  the  way  of  fault  scarps  and  gorges. 
Chmatic  changes,  on  the  contrary,  are  positively  known  to  have  taken  place,  for  no  one 
doubts  that  when  New  York  was  covered  with  ice  the  climate  of  Arizona  was  different 
from  what  it  is  to-day.  Furthermore,  climatic  changes  would  act  in  exact  agreement  with 
the  topography.  That  is,  if  a  mountain  range  were  high  and  massive,  and  a  change  of 
climate  toward  aridity  were  to  kill  a  large  amount  of  vegetation  upon  its  sides,  much 
soil  and  gravel  would  be  washed  down  and  deposited  at  the  base.  A  return  of  moist  con¬ 
ditions,  on  the  contrary,  would  lengthen  the  streams  and  cause  channeling.  Thus  high, 
steep  mountains  would  be  accompanied  by  lofty  terraces.  In  the  case  of  low,  gently  rounded 
hills,  on  the  other  hand,  aridity  might  cause  the  death  of  vegetation,  but  the  soil  would  not 
be  washed  away  with  anything  like  such  great  rapidity  as  upon  mountains  of  steeper  slope. 
Thus  no  terraces,  or  only  low  ones,  would  be  formed.  Every  part  of  a  region  would 
be  acted  upon  equally,  without  respect  to  the  topography  or  to  the  direction  or  size  of  the 
streams,  and  the  effect  would  everywhere  be  of  the  same  kind,  yet  the  results  would  vary 
in  harmony  with  the  topography.  Altogether  it  seems  as  if  the  climatic  theory  fitted  all 
the  facts  so  far  as  they  are  yet  known,  while  the  theory  of  earth  movements  meets  obstacles 
at  every  point.  The  matter  still  needs  a  vast  amount  of  study,  however,  especially  along 
the  lines  of  a  careful  mapping  and  measuring  of  the  terraces  of  a  few  chosen  regions.  Much 
light  might  also  be  obtained  by  a  careful  investigation  of  the  many  channels  which  have 
been  cut  by  various  rivers  since  the  opening  of  the  Southwest  to  settlement  by  the  white 
man. 

THE  CORRELATION  OF  TERRACES. 

If  the  theory  of  the  climatic  origin  of  terraces  be  accepted,  we  are  at  once  confronted 
by  the  problem  of  the  correlation  of  those  in  various  parts  of  the  world.  As  yet  it  is  too 
early  to  attempt  much  along  this  line.  Nevertheless,  it  is  worthy  of  note  that  in  number, 
arrangement,  degree  of  weathering,  and  other  characteristics,  there  seems  to  be  a  fairly 
close  agreement  between  those  of  America  and  of  Asia.  Undoubtedly  the  number  of 
terraces  varies  considerably,  but  the  variation  apparently  follows  well-defined  rules.  In 
general  the  number  is  greatest  among  lofty  mountains  in  regions  of  pronounced  aridity. 
Where  the  relief  diminishes,  or  where  the  climate  is  less  arid,  either  because  of  greater 
precipitation  or  because  of  lower  temperature  and  less  evaporation,  the  number  of  terraces 
becomes  less.  In  the  districts  of  maximum  development,  such  as  the  higher  mountains 
of  southern  Arizona  or  the  lofty  mountains  of  Central  Asia,  the  common  number  is  five. 
Elsewhere  it  diminishes  to  two.  Such  a  discrepancy  does  not  mean  a  different  periodicity 
in  the  various  regions.  It  simply  indicates  that  from  the  geological  point  of  view  terraces 
are  ephemeral.  In  regions  where  the  mountains  are  low  the  amount  of  deposition  may  be 
so  small  that  terraces  of  different  ages  appear  as  parts  of  a  single  formation,  or  the  entire 
body  of  some  terraces  may  be  carried  away  by  erosion.  In  regions  of  only  slight  aridity 
erosion  may  be  so  active  during  the  erosive  portion  of  a  terrace  cycle  that  all  the  deposits 
are  carried  away.  That  such  occurrences  take  place  is  proved  by  the  fact  that  even 
where  the  maximum  number  of  terraces  is  found  in  some  valleys,  others  in  close  proximity 
show  only  two  or  three.  Moreover,  in  a  single  valley  some  portions  have  five  terraces, 
and  others  only  two,  three,  or  four.  One  can  often  trace  a  terrace  upstream  and  actually 
see  it  disappear,  either  coming  to  an  abrupt  head,  coalescing  with  an  adjacent  terrace,  or 
simply  being  lost  by  erosion. 

The  alluvial  terraces,  both  of  Asia  and  America,  are  evidently  due  to  a  series  of  changes 
of  decreasing  intensity.  The  first  suggestion  that  presents  itself  is  that  they  may  repre¬ 
sent  the  various  epochs  of  the  glacial  period.  This  does  not  seem  probable,  however.  In 
the  first  place,  the  youngest  terraces  are  far  too  new  to  have  anything  to  do  with  the 
last  glacial  epoch.  In  the  second  place,  there  is  too  much  difference  in  size  between  the 


36 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


first  and  the  last  to  permit  the  supposition  that  each  of  them  represents  a  main  epoch. 
Finally,  the  oldest  terrace  does  not  show  sufficient  signs  of  age  to  warrant  the  belief  that  it 
is  as  old  as  the  first  of  the  known  glacial  epochs  of  the  Pleistocene  period.  It  is  much  worn 
and  eroded  almost  ever3rwhere,  and  in  many  places  it  has  been  entirely  removed,  but  its 
materials  are  weathered  and  decayed  to  only  a  moderate  degree.  It  seems  probable, 
therefore,  as  Penck  has  suggested  in  regard  to  those  of  Asia,  that  the  oldest  terrace  may 
represent  the  last  glacial  epoch,  and  that  the  others  represent  the  post-glacial  stages,  or 
minor  epochs  of  glacial  retreat,  of  which  there  is  an  ever-increasing  abundance  of  evidence, 
not  only  in  the  Alps  and  Scotland  and  other  parts  of  Europe,  but  in  America.  Inasmuch 
as  man  is  known  to  have  existed  prior  to  the  last  great  glacial  epoch,  the  terraces,  if  our 
conclusions  are  correct,  preserve  the  record  of  a  series  of  climatic  changes  which  have  played 
a  part  in  shaping  human  destiny.  If  the  oldest  terrace  dates  back  no  more  than  30,000 
years,  more  or  less,  to  the  last  glacial  epoch,  the  youngest  can  not  be  more  than  2,000  or 
3,000  years  old  at  most,  and  may  be  much  less. 


CHAPTER  V. 


THE  FLUCTUATIONS  OF  THE  OTERO  SODA  LAKE. 

Variations  in  the  level  of  lakes  without  outlets  are  universally  recognized  as  one  of 
the  easiest  and  most  accurate  methods  of  determining  changes  of  climate.  The  well-known 
monographs  of  Gilbert  and  Russell  on  Lakes  Bonneville  and  Lahontan  have  shown  that 
during  the  glacial  period  the  inclosed  salt  lakes  of  Utah  and  Nevada  expanded,  apparently 
by  reason  of  the  same  increase  of  precipitation  or  decrease  of  temperature  which  caused 
the  formation  of  the  vast  continental  glaciers  of  northeastern  America  and  northwestern 
Europe.  Further  researches  have  proved  that  other  salt  lakes,  not  only  in  the  arid  South¬ 
west  of  the  United  States,  but  throughout  Asia,  expanded  similarly.  Many  of  the  old 
lake  basins,  however,  even  in  America,  have  not  been  accurately  described  as  yet ;  and  in 
most  of  them  little  attention  has  been  paid  to  evidences  of  minor  fluctuations  since  the 
last  great  expansion,  which  presumably  took  place  synchronously  with  the  last  or  Wisconsin 
advance  of  the  ice-sheet.  Evidences  of  such  minor  fluctuations  exist  in  various  places, 
one  of  which,  the  Otero  Soda  Lake,  will  be  described  in  this  chapter.  Unfortunately  in 
this  case,  as  in  almost  all  others,  we  have  no  means  of  assigning  exact  dates  to  the  various 
stages  of  the  lake.  The  only  North  American  lakes  where  that  is  yet  possible,  even  in  the 
most  imperfect  degree,  appear  to  be  those  of  the  group  immediately  surrounding  the  City 
of  Mexico.  They  will  be  considered  later,  in  a  chapter  devoted  to  Mexico.  Meanwhile 
we  shall  direct  our  attention  to  the  minor  fluctuations  of  the  Otero  Soda  Lake  and  to  the 
accompanying  formation  of  large  expanses  of  gypsum  dunes.  We  shall  find  that  these 
indicate  that  the  change  from  the  climate  of  the  last  glacial  epoch  to  that  of  the  present 
does  not  appear  to  have  proceeded  by  regular  steps  according  to  the  old  supposition.  On 
the  contrary  it  seems  to  have  been  marked  by  pronounced  pulsations.  The  minor  strands 
apparently  do  not  mark  mere  stages  of  retrogression,  but  distinct  periods  of  advance 
separated  by  times  when  the  water  fell  to  decidedly  low  levels. 

Before  discussing  the  features  which  bear  on  our  immediate  problem  of  recent  climatic 
changes,  a  short  description  of  the  Otero  Basin  in  general  will  be  in  order,  partly  to  give 
the  setting  of  what  follows,  and  partly  because  this  region  has  been  discussed  relatively 
little.  My  study  of  the  basin  in  the  spring  of  1911  was  made  in  company  with  Mr.  E.  E. 
Free,  who  at  that  time  was  engaged  in  an  investigation  of  potash  deposits  on  behalf  of 
the  Bureau  of  Soils  of  the  United  States  Department  of  Agriculture.  I  have  drawn  freely 
on  his  observations  and  on  the  results  of  his  work.*  I  take  pleasure  in  here  expressing  my 
thanks  for  his  courtesy. 

The  Otero  Basin  lies  at  an  altitude  of  a  little  over  4,000  feet  between  two  ranges  of 
fault-block  mountains  in  the  central  part  of  southern  New  Mexico.  The  mountains  run 
north  and  south,  and  may  be  considered  as  disconnected  continuations  of  the  eastern 
portion  of  the  Rockies.  The  eastern  range  has  an  altitude  of  about  9,000  feet  in  the 
Mescalero  portion  near  the  Otero  Lake,  while  farther  north  in  Sierra  Blanco,  or  Capitan,  it 
rises  to  13,000.  The  range  is  bounded  on  the  west — that  is,  on  the  side  toward  the  basin — 
by  a  steep  fault  scarp.  At  the  top  lies  the  maturely  dissected  plateau  described  in  the  pre¬ 
ceding  chapter  on  the  physiographic  form  of  the  land.  Toward  the  north  the  plateau 
rises  into  the  well-dissected  slopes  of  Sierra  Blanco,  while  toward  the  east  it  falls  off  gradu¬ 
ally  to  the  Staked  Plains  of  eastern  New  Mexico  and  western  Texas.  With  these  portions. 


*  E.  E.  Free:  The  topographic  features  of  the  desert  basins  of  the  United  States.  Bui.  54,  U.  S.  Dept.  Agr.,  1914. 

37 


38 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


however,  we  are  not  concerned.  The  fault  scarp  which  forms  the  immediate  eastern 
boundary  of  the  Otero  Basin  must  limit  our  investigations.  This  escarpment  shows 
evidence  of  two  great  periods  of  faulting  and  one  minor  period.  Inasmuch  as  the  strata 
of  the  uppermost  parts  of  the  plateau  are  Permian,  the  earliest  faulting  may  have  taken 
place  in  the  Triassic  or  Jurassic  eras.  Cretaceous  strata,  however,  lie  on  the  back  slope 
of  the  plateau.  Hence  the  main  faulting  can  not  have  taken  place  until  late  in  that  era 
or  in  the  Tertiary.  After  its  occurrence  the  uplifted  region  was  worn  to  a  condition  of  matu¬ 
rity,  after  which  it  was  again  raised  by  pronounced  faulting  at  some  time  in  the  Tertiary 
era.  This  movement,  however,  by  no  means  brought  the  plateau  to  its  present  level. 
This  was  not  accomplished  until  the  original  fault  scarp  had  been  dissected  into  deep 
valleys,  its  top  had  been  battered  back  2  or  .3  miles  from  its  original  position,  and  its  foot 
had  been  concealed  under  a  deep  apron  of  piedmont  gravels.  Then  renewed  faulting 
occurred  and  the  piedmont  gravels  were  cut  in  two,  probably  along  nearly  the  same  line 
where  the  original  faulting  had  taken  place.  To-day  the  old  piedmont  gravels  of  the 
uplifted  block  can  be  seen  as  a  much  dissected  terrace  lying  at  an  altitude  of  about  1,000 
feet  above  the  edge  of  the  present  plain.  Below  the  terrace  the  topography  is  highly 
rugged  and  youthful;  above  it,  for  a  space,  the  topography  is  still  somewhat  rugged  and 
may  be  considered  in  the  early  stages  of  maturity;  while  still  higher,  upon  the  main  pla¬ 
teau,  as  we  have  seen  in  an  earlier  chapter,  it  is  thoroughly  mature.  The  date  of  this  last 
main  faulting  must  be  somewhere  in  the  late  Tertiary,  but  the  process  is  probably  not  yet 
complete.  At  the  very  base  of  the  escarpment,  from  Alamogordo  on  the  south  to  La  Luz, 
5  miles  to  the  north,  I  traced  a  little  fault  scarp  of  very  recent  origin,  and  further  investi¬ 
gation  would  probably  show  that  it  extends  much  farther.  The  movement  at  the  time 
of  the  last  faulting  was  in  the  same  direction  as  during  the  major  faul tings  of  earlier 
times,  that  is,  the  eastern  side  was  uplifted.  The  piedmont  deposits  at  the  base  of  the 
mountains  were  cut  in  two,  and  the  eastern  part  now  stands  from  10  to  20  feet  higher 
than  the  western.  Taken  as  a  whole,  the  phenomena  of  the  eastern  side  of  the  Otero  Basin 
are  surprisingly  hke  those  of  the  eastern  side  of  the  basin  of  old  Lake  Bonneville,  at  the 
base  of  the  Wasatch  Mountains  near  Salt  Lake  and  Ogden.  In  other  respects,  also,  the 
two  basins  show  marked  similarity. 

On  the  west  side  of  the  Otero  Basin  the  San  Andreas  Mountains  (and  also  apparently 
the  Organ  Range,  farther  to  the  south)  assume  the  form  of  sharply  tilted  fault  blocks,  with 
a  precipitous  escarpment  forming  the  front  slope  and  facing  toward  the  east.  The  tops 
of  highly  inclined  Pennsylvanian  limestones  form  the  back  slope  which  descends  to  the 
Journada  del  Muerto  east  of  the  Rio  Grande.  Here  the  tilting  of  the  block  has  been  so 
great  that  all  semblance  of  a  plateau  or  of  an  earlier  topography  has  been  destroyed. 

The  floor  of  the  Otero  Basin  has  been  deeply  covered  with  deposits  just  as  has  the 
floor  of  practically  every  basin  in  arid  regions.  The  total  depth  of  the  filling  is  unknown, 
but  a  railroad  well  at  Alamogordo,  near  the  edge  of  the  basin,  was  sunk  to  a  depth  of  1,004 
feet  without  reaching  the  bottom  of  the  irregular  succession  of  thin  beds  of  fine  gravel, 
sand,  and  clay  which  compose  the  greater  part  of  the  basin  deposits.  These  deposits 
now  form  a  large  plain,  very  flat  in  the  center  and  rising  gently  toward  the  edges,  where 
the  materials  change  from  sahne  deposits,  silt,  and  clay  to  gravel.  The  width  of  the 
basin  from  east  to  west  is  about  40  miles  in  the  widest  part;  the  length  is  over  100  miles. 
On  the  south  the  plain  rises  gently  to  a  flat  divide  and  then  falls  away  once  more  toward 
El  Paso  and  the  Rio  Grande.  On  the  north  it  rises  more  rapidly  after  the  main  level 
portion  has  been  left  behind,  and  ultimately  it  merges  with  the  great  plateau  of  central 
New  Mexico.  The  main  line  of  drainage  from  the  plateau  to  the  basin  floor  is  occupied 
by  a  very  recent  lava  flow  which  has  sometimes  been  supposed  to  date  back  no  farther 
than  the  beginning  of  historic  times.  It  begins  in  the  vicinity  of  Carizozo  and  continues 
southward  nearly  60  miles. 


THE  FLUCTUATIONS  OF  THE  OTERO  SODA  LAKE. 


39 


Manifestly  a  basin  such  as  that  of  Otero  must  contain  a  lake  if  the  rainfall  is  sufficiently 
heavy.  Since  the  total  precipitation  of  this  region,  however,  is  only  10  inches  per  year 
on  an  average,  and  since  the  filling  of  the  basin  with  waste  has  made  the  bottom  very  flat, 
no  permanent  lake  can  now  exist.  The  water  which  runs  down  from  the  mountains  during 
the  winter  rainy  season  or  during  the  sudden  thunder-showers  of  summer  spreads  out  in 
shallow  sheets  and  soon  evaporates.  The  so-called  Otero  Soda  Lake  is  really  one  of  a  series 
of  large  playas  having  a  length  of  about  40  miles  north  and  south,  and  a  width  of  6  miles 
or  more.  On  all  sides  except  the  west  other  smaller  playas,  several  times  in  a  year,  are 
similarly  filled  with  water  which  soon  evaporates,  leaving  white  plains  of  soda  and  gypsum. 
During  the  glacial  period  the  area  covered  by  all  the  playas  appears  to  have  been  included 
within  a  single  great  lake,  which  was  probably  60  miles  long  and  30  wide.  The  evidence 
for  this  is  found  in  certain  old  strands,  plainly  visible  at  the  base  of  the  San  Andreas  Moun¬ 
tains  on  the  west  side  of  the  basin.  These  have  never  been  studied  with  care,  and  my 
visit  was  too  brief  to  allow  of  more  than  a  cursory  examination.  They  are  visible  in  many 
places,  however,  and  can  be  seen  extending  almost  unbroken  for  20  miles  or  more.  The 
lowest  and  most  prominent  lies  over  200  feet  above  the  present  level  of  the  main  playa. 
Above  it  at  intervals  of  from  40  to  80  feet  three  others  can  be  seen.  On  the  east  side  of 
the  basin  none  of  the  old  strands  are  visible.  Possibly  they  were  small  and  insignificant 
because  of  the  extremely  gentle  slope  of  the  plain  on  this  side,  and  have  been  concealed  by 
the  large  amount  of  debris  which,  since  their  formation,  has  been  washed  down  from  the 
high  plateau.  Even  on  the  west  side,  where  the  mountains  are  far  lower  and  less  extensive 
than  the  plateau  to  the  east,  great  fans  of  gravel  have  been  washed  out  from  all  the  canyons, 
burying  the  bottoms  of  the  cliffs  along  the  old  strands,  and  in  many  cases  completely 
concealing  the  cliffs  themselves.  This  subject,  together  with  that  of  a  possible  outlet  to 
the  south  at  the  time  of  the  lake’s  greatest  expansion,  must  be  left  for  future  study;  so,  too, 
must  the  interesting  question  of  the  relation  of  the  more  recent  phases  of  faulting  and 
uplift  to  the  times  of  expansion  of  the  ancient  lake.  All  these,  important  as  they  are,  do 
not  bear  on  our  present  problem.  The  one  essential  fact  is  that  the  old  strands  seem  to 
furnish  strong  evidence  that  in  former  times  the  basin  was  occupied  more  than  once  by 
a  lake  whose  extent  was  far  greater  than  that  of  the  present  playas.  Almost  without 
further  proof  we  may,  I  think,  assume  that  the  epochs  of  expansion  must  have  coincided 
with  the  glacial  epochs  of  more  northern  regions.  The  importance  of  this  lies  in  its  indica¬ 
tion  that  during  the  glacial  period  the  climate  of  North  America  changed  almost  as  much 
in  the  warmer,  drier  portions  of  the  continent  as  in  the  colder,  moister  portions.  We 
can  not  yet  say  with  assurance  whether  the  strands  represent  the  main  epochs  of  the 
glacial  period,  or  whether,  as  is  more  likely,  at  least  part  represent  the  well-known  post¬ 
glacial  stages  which  have  been  so  much  studied  of  late  in  the  Alps,  Scotland,  and  elsewhere. 
Whatever  be  their  exact  age,  it  is  evident  that  they  belong  to  the  most  recent  geological 
times,  and  that  any  changes  which  have  taken  place  since  their  formation  are  sufficient!}^ 
recent  to  fall  within  the  period  of  man’s  probable  presence  in  America. 

Unmistakable  evidence  that  such  changes  have  actually  occurred  in  the  most  recent 
post-glacial  times  is  found  in  certain  minor  strands  of  the  old  lake  and  in  a  series  of  gypsum 
dunes  of  various  ages.  When  the  playa  or  Soda  Lake  is  at  its  greatest  extent,  its  temporary 
waters  are  deep  enough  to  be  raised  by  the  wind  into  little  waves  of  sufficient  strength  to 
cut  a  tiny  bluff,  which  at  the  southeastern  corner  of  the  playa  has  a  height  of  about  2  feet. 
Above  the  little  bluff  lies  a  terrace  100  to  200  feet  wide.  Like  the  bottom  of  the  playa 
itself,  the  terrace  is  covered  with  crystals  of  soda  and  gypsum,  but  these  saline  deposits 
are  not  fresh  like  those  of  the  playa,  and  they  are  studded  with  vegetation,  indicating  a 
considerable  lapse  of  time  since  their  deposition.  At  rare  intervals  the  water  may  even 
now  come  up  over  this  terrace,  but  scarcely  for  long  enough  periods  or  to  sufficient  depth 
to  allow  the  waves  to  cut  so  steep  and  pronounced  a  bluff  as  that  which  rises  to  a  height 


40 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  15  or  16  feet  back  of  the  terrace.  Therefore  we  infer  that  at  some  time  not  more  than  a 
few  hundred  years  ago  the  water  must  have  stood  higher  than  now,  and  at  such  a  level  as 
to  cover  the  terrace  and  cut  a  well-defined  bluff  at  a  level  about  4  feet  above  that  of  the 
floor  of  the  playa.  If  the  lake  rose  to  this  level  it  must  have  contained  water  most  of  the 
time,  for  it  would  scarcely  be  possible  every  year  for  evaporation  to  remove  4  feet  of  water 
in  the  few  months  which  intervene  between  the  end  of  one  rainy  season  and  the  time 
when  the  lake  would  be  replenished  by  the  rains  of  the  succeeding  season,  whether  it  be 
summer  or  winter. 

The  top  of  the  bluff  overlooking  the  4-foot  strand  forms  another  terrace,  like  the  one 
above  the  present  strand,  but  much  older  and  more  covered  with  vegetation.  Back  of 
this,  and  at  an  altitude  of  about  20  feet  abo.ve  the  floor  of  the  playa,  a  third  small  bluff 
rises  about  10  feet.  It  clearly  marks  the  strand  along  which  the  lake  rested  at  some  time 
hundreds  of  years  before  the  day  of  the  4-foot  strand.  At  that  time  the  lake  was  evidently 
much  larger  than  the  present  playa,  and  was  so  deep  that  it  can  not  possibly  have  been 
subject  to  complete  desiccation.  Back  of  the  20-foot  strand  there  may  possibly  be  still 
another  belonging  to  times  much  more  recent  than  the  main  strands  200  feet  or  more 
above  the  lake.  This  doubtful  third  member  of  the  group  of  minor  strands  lies  about 
60  feet  above  the  floor  of  the  playa.  I  saw  evidence  of  it  only  at  the  southeast  corner  of 
the  playa,  where  a  low  bluff  and  a  line  of  gypsum  dunes  run  parallel  to  the  present  shoreline 
at  a  distance  of  from  a  third  to  a  quarter  of  a  mile  from  it;  they  seem  to  indicate  another 
old  strand,  but  the  evidence  is  not  sufficiently  clear  to  permit  certainty.  Nevertheless, 
even  if  we  omit  the  60-foot  strand,  those  at  elevations  of  20  and  4  feet  are  sufficient  to 
show  that  in  times  long  after  the  end  of  the  glacial  period  the  Otero  Lake  has  varied  in 
size,  apparently  because  of  distinct  climatic  fluctuations.  The  strands,  however,  do  not 
suffice  to  show  whether  the  fluctuations  were  merely  pauses  on  the  way  toward  aridity 
or  were  distinct  periods  of  increased  moisture  following  times  of  aridity. 

The  most  peculiar  feature  of  the  Otero  Basin,  and  one  of  the  most  significant  from  a 
climatic  point  of  view,  is  the  unique  dunes  of  pure  white  gypsum,  the  “White  Sands,” 
as  they  are  called.  Along  the  east  side  of  the  main  playa  they  form  a  large  tract  nearly 
20  miles  long  and  10  wide  in  places.  The  dunes  are  like  the  ordinary  type  in  shape  and 
movement.  Their  peculiarity  consists  in  the  fact  that  they  are  composed  of  almost  pure 
gypsum,  which  gives  them  a  dazzling  white  appearance.  When  the  playas  become  dry 
in  the  rainless  foresummer  or  in  the  fall  the  strong  southwest  winds  which  then  prevail 
sweep  across  the  smooth  expanses  and  pick  up  clouds  of  gypsum  crystals  which  have 
been  laid  down  by  the  diminishing  water.  These  are  swept  beyond  the  limits  of  the 
playas  and  are  there  heaped  up  into  dunes  ranging  from  5  to  40  feet  in  height.  In  course 
of  time  the  dunes  are  gradually  moved  forward  by  the  winds,  while  new  ones  form  behind 
them.  At  present  the  area  of  fresh  dunes  is  constantly  increasing  by  the  blowing  forward 
of  the  gypsum  sands.  For  example,  at  the  plaster  mill  a  few  miles  southeast  of  Alamogordo, 
and  at  many  other  places  along  the  eastern  margin  of  the  dune  area,  the  sand  can  be  seen 
advancing  like  a  great  white  wall.  At  some  points  it  is  overwhelming  bushes  and  small 
trees,  which  in  many  cases  are  completely  buried,  only  to  reappear  at  length  behind  the 
dunes  when  the  winds  have  swept  the  gypsum  beyond  them.  At  other  points  the  White 
Sands  are  encroaching  upon  old  roads,  some  of  which  can  be  seen  buried  to  a  depth  of 
20  feet.  An  old  stage-driver  informed  Dr.  MacDougal  that  when  he  used  to  drive  the 
overland  stage  through  the  Otero  Basin  in  the  early  eighties  he  was  accustomed  to  water 
his  horses  at  a  well  on  the  eastern  edge  of  the  dune  area.  Now,  however,  the  well  is  hidden 
in  the  midst  of  the  moving  sand,  a  mile  or  more  from  the  margin. 

This  rapid  movement  of  the  dunes  does  not  appear  to  have  lasted  for  any  great  length 
of  time,  probably  for  no  more  than  a  few  score  or  a  hundred  years.  There  is  no  means, 
however,  of  judging  exactly  how  long  it  has  lasted,  but  if  there  has  been  an  advance  of  a 


THE  FLUCTUATIONS  OF  THE  OTERO  SODA  LAKE. 


41 


inile  in  scarcely  30  years,  it  seems  probable  that  the  dunes  would  have  spread  farther  than 
the  present  limits  if  equally  favorable  conditions  had  prevailed  for  any  great  length  of  time. 

The  part  of  the  White  Sands  which  is  now  advancing  is  not  the  main  body  of  the  dunes, 
but  merely  a  small,  superficial  portion.  The  main  body  is  of  the  same  type  as  the  portions 
now  in  motion,  but  the  sands  are  partially  fixed  by  scattered  bushes  and  other  small  forms 
of  vegetation.  Therefore  they  do  not  move.  In  some  places  it  can  be  seen  that  in  recent 
times  certain  portions  of  them  have  been  freed  from  the  restraint  of  vegetation,  and  have 
begun  to  move,  adding  their  quota  to  the  supply  of  sand  derived  from  the  gypsum  crystals 
of  the  floor  of  the  playa.  Clearly  the  older  portion  of  the  White  Sands,  which  is  decidedly 
the  major  portion,  was  at  one  time  in  motion.  At  that  time  the  climate  must  have  been 
approximately  as  dry  as  now.  Then  came  a  time  of  changed  conditions,  when  the  moving 
dunes  were  fixed.  In  certain  cases,  such  as  the  shores  of  the  Atlantic  Ocean  in  Massa¬ 
chusetts,  or  the  south  shore  of  Lake  Michigan,  dunes  become  fixed  because  they  are  driven 
so  far  from  the  source  of  supply  that  new  sand  is  not  furnished  in  sufficient  quantity  to 
prevent  the  growth  of  vegetation.  In  such  cases  the  dunes  close  to  the  abundant  and 
constantly  renewed  supply  of  sand  along  the  shore  can  not  become  covered  with  vegetation 
simply  because  there  is  such  a  constant  influx  of  sand,  although  vegetation  would  quickly 
appear  if  the  amount  of  sand  brought  in  by  the  waves  and  wind  should  diminish.  Conse¬ 
quently  we  find  the  dunes  more  and  more  covered  with  vegetation  as  we  proceed  inland, 
until  a  few  miles  back  from  the  coast  they  are  completely  fixed.  Among  the  White  Sands, 
on  the  contrary,  the  conditions  are  quite  different.  Here  there  is  no  gradation  from  fixed 
to  unfixed  dunes.  The  two  types  exist  side  by  side,  both  at  the  outer  edge  of  the  dune  area 
and  at  the  inner  edge  close  to  the  playa.  Everywhere  the  new  moving  dunes  are  over¬ 
riding  the  old  stationary  ones.  The  only  explanation  seems  to  be  either  that  the  supply 
of  gypsum  has  recently  increased  or  that  the  amount  of  vegetation  has  decreased  so  that 
the  fixed  dunes  have  in  part  become  free.  Either  alternative  demands  a  change  of  climate. 
The  supply  of  gypsum  would  be  greatly  increased  by  a  diminution  in  the  amount  of  water 
flowing  into  the  lake.  If  a  considerable  portion  of  the  floor  of  the  playa  were  covered 
with  water,  as  happened  at  the  time  of  the  formation  of  the  4-foot  strand,  the  supply  of 
gypsum  would  be  much  less  than  now,  for  at  present  practically  all  of  it  comes  from  the 
floor  of  the  playa  during  the  dry  season.  If  the  rainfall  were  great  enough  to  change 
the  playa  into  a  shallow  lake,  the  amount  of  moisture  among  the  dunes  would  probably 
be  so  great  as  to  cause  the  growth  of  vegetation,  and  thus  the  dunes  would  be  fixed.  In 
other  parts  of  the  world  such  an  increase  in  vegetation  followed  by  a  later  decrease  seemy 
to  be  sufficient  to  cause  the  fixation  and  freeing  of  dunes  without  any  change  in  the  suppls 
of  sand.  I  have  seen  instances  of  this  in  several  places,  especially  in  the  desert  south  of 
Palestine  near  Beersheba,  and  on  the  borders  of  the  great  desert  of  Transcaspia.  Whether 
the  twofold  aspect  of  the  White  Sands  is  due  chiefly  to  a  change  in  the  supply  of  gypsum  or 
to  a  variation  in  the  amount  of  vegetation,  its  ultimate  cause  seems  to  be  the  same.  The 
older  phase  seems  to  indicate  a  period  of  aridity  much  like  the  present;  the  fixation  of  the 
dunes  apparently  points  to  a  greater  supply  of  water  and  a  higher  stand  of  the  lake;  and  the 
free  dunes  of  the  present  are  in  motion  because  the  climate  is  dry,  the  lake  has  become  a 
playa,  and  the  amount  of  vegetation  is  hmited.  Here,  then,  we  seemingly  have  evidence 
that  the  last  series  of  climatic  changes  has  not  been  a  mere  increase  in  aridity,  broken  by 
a  period  of  uniformity,  but  has  been  a  pulsation  from  dry  to  moist  and  back  again  to  dry. 

Two  deposits  of  gypsum  older  than  those  just  discussed  appear  to  be  the  remains  of 
earlier  fields  of  dunes,  which  in  their  day  were  like  the  present  White  Sands.  One  of  them, 
called  by  Mr.  Free  the  Intermediate  Gypsum,  still  shows  the  characteristic  topography  of 
dunes,  together  with  occasional  traces  of  cross-bedding.  It  covers  about  the  same  area 
as  the  modern  Sands,  and  can  frequently  be  seen  coming  out  from  under  them  and  extending 
for  half  a  mile  or  so.  The  sharper  forms  of  the  dunes  have  been  smoothed  off,  and  a  con- 


42 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


siderable  amount  of  solution  has  removed  much  of  the  gypsum  from  the  outer  surface, 
leaving  only  the  impurities  in  the  form  of  soil.  On  the  gent’e  slopes  thus  formed,  and  in 
the  small  but  important  supply  of  soil,  vegetation  of  a  grassy  type  has  established  itself 
and  is  able  to  persist  even  in  a  dry  time  like  the  present. 

Underneath  the  Intermediate  Gypsum  lies  the  Tularosa  Gypsum,  as  it  has  been  named 
by  Mr.  Free.  In  this  the  typical  dune  topography  has  completely  disappeared,  as  has 
the  cross-bedding.  Nevertheless  the  eohan  origin  of  the  deposit  is  quite  well  established 
by  the  sun-cracks,  rounded  grains,  and  other  characteristics  which  Mr.  Free  has  detected 
under  the  microscope.  The  Tularosa  Gypsum  is  much  more  extensive  than  the  others. 
On  the  east  it  extends  nearly  to  the  foot  of  the  mountains  and  is  often  found  buried  under 
a  thin  layer  of  alluvium  recently  brought  down  from  the  mountains.  A  similar  deposit, 
but  probably  of  considerably  greater  age,  is  also  found  high  on  the  flanks  of  the  fault  scarp 
which  bounds  the  Otero  Basin  on  the  east.  It  forms  part  of  the  old  basin  deposit  of  pied¬ 
mont  gravel,  silt,  and  clay  which  was  uphfted  1,000  to  2,000  feet  at  the  time  when  the 
last  great  fault  occurred. 

Two  possibilities  suggest  themselves  in  regard  to  the  origin  of  the  Intermediate  and 
Tularosa  beds  of  gypsum:  The  first  is  obviously  that  they  indicate  periods  of  aridity  like 
the  present,  and  that  their  relation  to  one  another  and  to  the  later  gypsum  is  the  same 
as  that  of  the  free  and  the  fixed  portions  of  the  White  Sands.  The  other,  suggested  by 
Mr.  Free,  is  that  the  older  dunes  were  formed  as  a  narrow  strip  on  the  immediate  edges 
of  a  lake  which  was  in  gradual  process  of  desiccation.  As  the  lake  retreated  it  was  always 
bordered  by  a  strip  a  mile  or  two  wide  where  it  had  laid  down  gypsum.  From  this  a 
narrow  band  of  dunes  was  formed.  The  dunes  quickly  became  fixed  by  vegetation,  since 
the  climate,  as  indicated  by  the  size  of  the  lake,  was  moister  than  now.  Thereafter  they 
remained  unchanged  except  for  the  normal  processes  of  weathering.  On  the  lakeward 
side  new  dunes  were  continually  in  process  of  formation,  followed  by  fixation,  thus  con¬ 
tinually  broadening  the  dune  area  in  proportion  to  the  retreat  of  the  lake.  Inasmuch  as 
we  can  not  follow  the  Intermediate  and  Tularosa  gypsums  under  the  White  Sands  we 
can  not  tell  whether  they  extend  as  far  as  the  borders  of  the  modern  playa,  nor  can  we 
ascertain  whether  in  the  interval  between  their  formation  the  lake  expanded.  Hence  we 
can  not  choose  between  the  two  theories.  The  fact  that  the  two  divisions  of  the  White 
Sands  apparently  represent  distinct  pulsations  rather  than  pauses  in  climatic  change  affords 
a  presumption  that  the  same  is  true  in  the  other  cases. 

CONCLUSION. 

The  general  conclusion  of  the  whole  may  be  summed  up  in  the  words  of  Mr.  Free  in 
the  report  already  referred  to : 

“The  whole  history  of  Lake  Otero  and  of  the  period  since  its  disappearance  is  a  record  of 
great  and  continuous  climatic  changes,  with  major  fluctuations  indicated  by  the  variations  of 
the  great  ancient  lake  and  its  deposits.  On  these  fluctuations  are  superposed  many  series  of 
minor  pulsations,  the  greater  of  which  can  be  read  in  the  triple  record  of  changing  topography 
in  lake,  dunes,  and  arroyos.  To  assign  a  time  scale  to  these  various  changes  and  to  date  them 
in  years  or  centuries  is  not  easy,  but  it  is  probable  that  something  can  be  done  by  careful  com¬ 
parative  study  of  various  lines  of  evidence  and  of  various  regions.  In  general  it  can  be  said  that 
the  Otero  Basin  shows  the  kind  of  climatic  fluctuations  which  Huntington’s  work  has  shown  to 
be  typical,  namely,  large,  long-period  pulsations,  upon  which  are  superposed  series  after  series 
of  smaller  pulsations  of  less  and  less  amplitude  and  shorter  and  shorter  period.” 


CHAPTER  VI. 

THE  RELATION  OF  ALLUVIAL  TERRACES  TO  MAN. 

From  the  purely  physical  phenomena  of  fluvial  terraces,  lacustrine  strands,  and  sand- 
dunes  we  have  been  led  to  a  broad  generalization  as  to  the  pulsatory  nature,  decreasing 
intensity,  and  present  continuance  of  post-glacial  changes  of  climate  in  the  arid  portions 
of  America.  From  the  same  lines  of  evidence  a  similar  conclusion  has  been  reached  as 
to  the  temperate  portions  of  Asia  and  the  lands  surrounding  the  Mediterranean  Sea.  In 
the  Old  World,  however,  it  has  been  possible  to  supplement  physical  evidence  by  a  large 
body  of  historical  and  archeological  data,  together  with  traditions  and  legends,  and  thus 
to  determine  the  approximate  dates  of  some  of  the  main  climatic  events  and  to  discover 
some  of  their  effects  upon  man.  In  general  we  are  probably  safe  in  assuming  that  the 
effect  of  a  given  type  of  change  upon  man  will  be  essentially  the  same  in  corresponding 
parts  of  the  two  hemispheres,  but  this  needs  careful  testing.  The  Asiatic  dates,  on  the 
other  hand,  do  not  necessarily  afford  any  clue  whatever  to  the  dates  of  similar  climatic 
changes  in  America.  Hence  our  next  step  must  be  to  find  out  the  relation  of  man  to  the 
changes  of  climate  whose  existence  we  have  inferred  in  America  and  then  to  determine  the 
dates.  It  must  be  constantly  borne  in  mind  that  the  belief  that  changes  have  taken  place 
at  certain  times  and  in  certain  ways  in  the  Old  World  by  no  means  involves  a  similar  behef 
in  respect  to  the  New  World.  Three  possibilities  present  themselves.  In  the  first  place, 
granting  that  pulsatory  chmatic  changes  have  taken  place  in  both  hemispheres,  it  is 
possible  that  those  in  America  came  to  an  end  long  before  those  in  Asia  and  thus  had  no 
influence  either  upon  the  Europeans  who  came  in  the  wake  of  Columbus  or  upon  the  ancient 
inhabitants  who  preceded  them.  In  the  second  place,  changes  may  have  taken  place  in 
the  climate  of  both  hemispheres  similar  in  kind,  but  by  no  means  synchronously.  They 
may  even  have  been  of  opposite  types,  America  becoming  dry  when  Asia  became  moist, 
and  the  reverse.  Finally,  there  is  the  third  possibility  that  all  the  continents,  or  at  least  all 
the  temperate  regions  of  the  northern  hemisphere,  have  been  subject  to  the  same  type  of 
changes  at  essentially  the  same  times.  Leaving  the  matter  of  dates  for  future  consider¬ 
ation,  let  us  attempt  to  determine  whether  any  one  or  more  of  the  changes  of  climate  which 
we  have  inferred  to  have  taken  place  in  America  occurred  since  man  reached  a  stage  of 
culture  such  that  he  inhabited  permanent  villages  or  towns  whose  traces  still  remain. 
The  importance  of  this  subject  is  so  great  that  we  shall  investigate  it  at  length,  and  shall 
in  many  cases  enter  into  minute  details  of  evidence  in  widely  scattered  regions.  I  shall 
endeavor  to  set  forth  the  facts  in  such  a  way  that  the  reader  can  frame  his  own  answers 
to  three  chief  questions.  First,  has  the  climate  of  America  changed  since  the  primitive 
inhabitants  built  the  ruins  which  now  abound  in  the  Southwest  and  Mexico?  Second,  if 
it  has  changed,  do  the  ruins  show  evidence  of  changes  in  more  than  one  direction  or  at  more 
than  one  distinct  epoch?  And  third,  do  the  inferred  changes  seem  to  have  had  effects  at 
all  comparable  to  those  which  seem  to  have  taken  place  in  Asia? 

Let  us  first  take  up  the  specific  problem  of  the  relation  of  man  to  the  alluvial  terraces 
which  hold  so  important  a  place  among  the  purely  physical  evidences  of  pulsations.  If  we 
accept  the  theory  of  the  chmatic  as  opposed  to  the  tectonic  origin  of  the  terraces  of  the 
Southwest,  the  finding  of  pottery  or  other  traces  of  human  occupation,  either  within  the 
body  of  a  terrace  or  persistently  upon  some  terraces  and  not  upon  others,  may  be  sig¬ 
nificant.  In  regard  to  the  second  point,  the  finding  of  traces  of  human  occupation  on  some 

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THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


terraces  and  not  on  others,  the  data  are  too  scanty  to  warrant  any  conclusion.  My  own 
observation  shows  that  ruins  of  prehistoric  (pre-Columbian)  villages  are  rarely  found 
upon  the  present  alluvial  flats — that  is,  upon  the  plains  formed  by  the  rivers  in  the  most 
recent  period  of  deposition.  Except  far  downstream  in  the  neighborhood  of  broad  playas, 
ruins  of  any  great  age  appear  to  be  found  always  on  terraces  just  above  the  plains  of  fine 
silt.  This  fact,  however,  possesses  no  special  significance,  for  the  location  may  have  been 
determined  by  motives  of  sanitation  or  by  the  desire  not  to  encroach  upon  arable  land. 

The  location  of  buried  pottery  is  much  more  significant.  The  finding  by  Professor 
Forbes  of  ancient  pottery  under  10  feet  of  alluvium  in  the  banks  of  the  newly  formed  inner 
valley  of  the  Santa  Cruz  at  Tucson  has  already  been  mentioned.  Another  occurrence  of 
this  same  nature  is  described  by  Mindeleff  in  the  Thirteenth  Annual  Report  of  the  Bureau 
of  Ethnology,  1891-92,  pp.  239-240.  In  the  valley  of  the  lower  Verde,  one  of  the  northern 
tributaries  of  the  Gila,  the  river  has  recently  excavated  a  channel,  leaving  the  old  flood¬ 
plain  as  a  terrace,  just  as  in  the  case  of  the  Santa  Cruz.  While  the  process  of  erosion  was 
in  progress,  Mindeleff  was  so  fortunate  as  to  see  and  photograph  an  old  irrigation  canal 
which  had  been  buried  beneath  10  feet  of  alluvium,  and  was  now  once  more  exposed  by 
erosion,  only  to  be  washed  away  forever  in  the  course  of  a  few  months.  He  estimates  that 
the  silting  up  of  the  valley  bottom  and  the  burial  of  the  ditch  to  a  depth  of  10  feet  must 
have  taken  at  least  150  years,  and  may  have  taken  several  times  as  long.  How  long  a  time 
elapsed  between  the  completion  of  the  process  of  deposition  and  the  inception  of  erosion  is 
entirely  problematical.  It  may  have  been  anywhere  from  10  years  to  10  centuries. 

The  examples  thus  far  given  have  been  from  a  small  area  in  southern  Arizona.  (See 
map,  frontispiece.)  In  northern  New  Mexico,  400  miles  away,  I  chanced  upon  a  similar 
example.  About  6  miles  north  of  Santa  Fe  and  3  miles  south  of  the  modern  pueblo  village 
of  Tesuque,  Mr.  Vierra,  an  artist  of  Santa  Fe,  pointed  out  a  place  on  his  ranch  where  pottery 
and  ashes  have  been  buried  to  a  depth  of  6  feet  under  alluvium  and  have  since  been  exposed 
by  the  cutting  of  the  stream  to  a  depth  of  15  feet.  In  the  steep  face  of  the  terrace  thus 
formed  we  found  the  vestiges  of  human  occupation  so  thickly  scattered  as  to  show  that  once 
a  small  village  must  have  been  located  here.  It  stood  in  the  angle  between  the  main  Te¬ 
suque  stream  and  a  small  tributary  from  the  southwest,  and  pottery  is  found  in  the  terraces 
of  both  streams.  I  happened  at  the  time  to  be  with  Mr.  Kenneth  M.  Chapman,  secretary 
and  artist  of  the  School  of  American  Archeology  at  Santa  Fe.  He  kindly  examined  the 
pottery  and  states  that  it  belongs  to  the  present  Tesuque  type,  and  not  to  the  prehistoric 
Pajaritan  type  found  in  the  older  and  more  important  ruins  of  the  region.  This  means 
that  since  the  Tewa  stock,  to  whom  the  Tesuque  Indians  belonged,  came  to  this  region, 
probably  700  to  800  years  ago,  there  has  been  time  for  a  village  to  be  founded  and  occupied 
long  enough  to  form  an  accumulation  of  pottery  and  ashes.  Then  the  village  was  abandoned 
and  floods  covered  it  with  6  feet  of  silt,  after  which  the  streams  changed  their  mode  of 
action  sufficiently  to  cause  the  erosion  of  a  broad  inner  valley  and  the  formation  of  a  terrace 
15  feet  high.  We  can  not  say  with  assurance  that  man’s  actions  may  not  have  had  a  part 
in  causing  erosion  to  begin,  but  inasmuch  as  man  has  occupied  the  region  continuously 
from  the  times  of  the  Pueblo  Indians  through  that  of  the  Spaniards  and  Mexicans  to  that 
of  the  Americans,  the  relation  of  man  to  the  country  has  not  changed  in  any  such  sudden 
way  as  has  been  the  case  in  southern  Arizona.  Yet  even  there  we  saw  that,  although  man 
had  a  hand  in  causing  terracing,  he  served  chiefly  as  a  means  of  setting  natural  forces  in 
operation  rather  than  as  a  new  force.  Heavy  rains  were  needed  before  any  terracing  could 
take  place,  even  in  southern  Aiizona,  and  in  northern  New  Mexico  it  is  still  more  probable 
that  the  terracing  was  due  to  natural  changes  causing  variations  of  rainfall. 

As  a  final  example  of  the  relation  of  the  terraces  to  man  I  shall  describe  the  conditions 
in  the  Tularosa  Valley  of  southern  New  Mexico  in  the  plateau  east  of  the  Otero  Basin. 
The  valley  begins  a  few  miles  north  of  the  summer  resort  known  as  Cloudcroft,  and  extends 


THE  RELATION  OF  ALLUVIAL  TERRACES  TO  MAN. 


45 


northwestward  past  the  Indian  agency  of  Mescalero,  then  westward  and  finally  south- 
westward  to  the  edge  of  the  escarpment,  where  it  debouches  upon  the  plain  of  the  Otero 
Basin.  Throughout  its  course  it  is  characterized  by  alluvial  terraces.  In  the  upper,  more 
mountainous  portions  of  the  valley  the  number  of  terraces  reaches  five,  while  lower  down 
the  number  diminishes.  At  the  present  time  no  continuous  stream  flows  from  end  to  end 
of  the  valley,  although  temporary  streams  flow  for  short  distances  here  and  there.  At 
some  earlier  time  a  continuous  stream  probably  flowed  the  entire  length  of  the  valley, 
for  the  main  terraces  are  well  developed  and  continue  many  miles,  as  if  cut  by  a  strong 
flow  of  water.  When  such  a  flow  existed  the  valley  bottom  was  doubtless  occupied  by  a 
gravelly  river  channel  having  a  regular,  graded  slope  from  end  to  end.  Now,  however, 
under  the  influence  of  the  last  epoch  of  relatively  intense  aridity,  the  valley  floor  has  been 
filled  with  alluvium  in  such  a  way  as  to  produce  well-marked  irregularities.  Wherever  a 
tributary  has  brought  in  an  unusually  large  amount  of  waste,  the  feeble  stream  of  the  main 
valley  has  spread  this  downstream  for  a  short  distance,  but  has  been  unable  to  carry  it 
away.  In  the  deep  deposits  of  silt  and  gravel  thus  formed  the  water  of  the  main  stream 
sinks  into  the  alluvium  and  disappears,  only  to  come  to  the  surface  once  more  at  some 
point  where  the  depth  of  the  alluvium  is  less.  In  this  way,  as  will  readily  be  seen,  the 
valley  bottom  has  been  divided  into  a  series  of  relatively  level  portions  where  abundant 
alluvium  has  been  deposited,  and  a  series  of  relatively  steep  slopes  where  the  abundant 
supply  of  alluvium  has  ceased  and  the  stream  which  should  carry  it  away  has  disappeared. 
Often,  as  one  rides  down  the  valley,  a  plain  a  quarter  to  a  half  mile  wide  and  several 
miles  long  is  encountered,  which  seems  at  the  lower  end  to  drop  off  almost  in  a  slope  that 
would  be  called  steep.  The  effect,  indeed,  as  one  looks  down  the  valley  from  the  middle 
of  the  plain,  is  as  if  the  bottom  of  the  valley  were  genuinely  dropped  down  to  a  lower  level. 
Even  to  the  unscientific  observer  it  is  manifest  that  if  the  supply  of  water  should  be  sufficient 
to  maintain  a  continuous  stream,  erosion  would  at  once  attack  the  steep  slopes  between 
the  plains.  As  a  matter  of  fact  this  process  has  already  begun  within  the  last  2  or  3  decades. 
At  various  points  deep  gullies,  one  of  them  with  a  depth  of  nearly  50  feet,  have  been  cut, 
and  a  series  of  years  of  heavy  rainfall  would  cause  them  all  to  be  prolonged,  both  upstream 
and  down,  until  a  continuous  gully  was  formed.  The  succession  of  events  here  is  exactly 
the  same  as  in  the  Santa  Cruz  Valley,  near  Tucson,  hundreds  of  miles  to  the  west.  The 
chief  difference  is  that  here  the  part  played  by  man  is  relatively  unimportant :  even  without 
man’s  intervention  climatic  forces  have  begun  to  form  a  terrace.  Apparently  the  last 
quarter  of  a  century,  from  about  1885  onward,  has  been  a  period  when  heavy  rains  were 
on  the  whole  more  numerous  than  for  many  decades,  or  possibly  several  hundred  years 
previously. 

In  ancient  times  the  Tularosa  Valley  contained  at  least  two  villages.  One  of  these 
was  located  in  the  broadening  of  the  valley  where  the  Mescalero  Indian  agency  employs 
about  20  white  men  and  women  to  take  care  of  about  350  semi-nomadic  Apache  Indians. 
The  old  village  probably  contained  quite  as  many  people  as  the  modern  agency,  and 
possibly  more,  for  traces  of  pottery  can  be  seen  on  both  sides  of  the  valley.  The  other 
village,  which  I  did  not  visit,  is  said  to  be  located  about  12  miles  below  the  agency  and 
5  miles  above  the  modern  village  of  Tularosa,  which  lies  out  in  the  plain  at  the  mouth 
of  the  Tularosa  Valley.  Ruins  are  described  in  the  plain  also,  but  they  are  beyond  the 
limits  of  our  present  investigation. 

Nearly  2  miles  below  the  agency  the  valley  bottom  is  broken  by  one  of  the  relatively 
steep  slopes  described  above.  The  plain  below  the  slope  is  quite  flat  and  almost  swampy. 
It  is  cultivated,  however,  by  means  of  irrigation  from  a  small  spring,  and  with  a  little 
more  care  could  easily  be  made  highly  productive.  On  either  side  the  plain  is  bounded 
by  gravel  terraces,  20  or  30  feet  high.  At  the  base  of  the  northern  terrace,  near  the  upper 
end  of  the  plain,  Mr.  A.  M.  Blazer,  who  lives  a  little  way  up  the  vaUey,  pointed  out  the 


46 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


ruins  of  an  ancient  canal.  Originally  it  appears  to  have  been  a  simple  ditch,  but  now  it  is 
a  mass  of  calcareous  tufa  about  3  feet  wide,  4  feet  thick,  and  hundreds  of  feet  long.  Its 
top  is  grooved  to  a  depth  of  about  a  foot,  and  the  sides  of  the  groove  have  a  thickness  of 
about  6  inches.  Its  upper  end  is  lost  in  the  plain,  either  having  been  bmied  or  eroded 
away.  The  lower  end  disappears  under  a  road  which  runs  nearly  parallel  to  the  ditch. 
Beyond  the  road  it  can  not  be  detected  and  has  probably  been  entirely  removed  by  erosion. 
The  peculiar  feature  of  the  ditch  is  that  it  was  not  built  to  water  the  plain.  If  that  had  been 
its  purpose  it  would  have  been  carried  along  the  foot  of  the  terrace.  Instead  of  this  it  was 
carried  along  the  face  of  the  terrace  with  as  little  slope  as  possible,  so  that  it  gradually 
leaves  the  plain  and  approaches  the  top  of  the  terrace,  which,  of  course,  has  a  steady  slope 
downstream.  The  ditch  must  have  been  designed  to  irrigate  the  top  of  the  terrace,  which 
it  would  reach  about  half  a  mile  downstream.  There,  as  pointed  out  by  Mr.  Blazer, 
a  tract  of  400  to  500  acres  could  be  irrigated.  This  land  is  now  unused,  partly  because  it 
is  surrounded  and  somewhat  dissected  by  gullies,  and  still  more  because  after  the  bottom 
lands  have  been  irrigated  there  is  not  enough  water  left  to  make  it  worth  while  to  build 
a  ditch  to  irrigate  the  terraces.  The  ditch  was  clearly  in  use  for  a  long  time,  long  enough 
at  least  to  allow  the  water  of  the  spring  to  deposit  from  2  to  4  feet  of  calcareous  tufa. 
Moreover,  it  was  carefully  engineered,  with  a  slope  as  gentle  as  possible,  and  apparently 
with  many  windings.  To-day  the  windings  would  almost  preclude  the  construction  of 
such  a  ditch  unless  masonry  were  employed,  but  in  the  days  when  it  was  built  the  tributary 
gullies  had  probably  not  been  cut  to  such  depth  as  now. 

The  phenomena  of  the  old  canal  imply  conditions  different  from  those  of  to-day.  Two 
possibilities  present  themselves.  In  the  first  place,  the  bottom  lands  may  have  been 
essentially  the  same  as  now,  but  the  population  was  so  dense  that  all  this  land  was  used 
and  more  was  needed.  Therefore  an  attempt  was  made  to  utilize  poorer  land  lying  on 
the  terrace.  The  attempt  was  successful,  as  is  evident  from  the  thickness  of  the  tufa, 
which  implies  long  use  of  the  canal.  The  amount  of  land  in  question  would  have  made 
such  an  attempt  well  worth  while.  According  to  Mr.  Blazer,  the  total  amount  would  be 
about  half  as  much  as  is  now  under  cultivation  in  the  entire  valley,  including  all  at  this 
village  and  at  the  lower  ruin,  12  miles  away.  The  size  of  the  canal  indicates  that  it  carried 
approximately  the  same  amount  of  water  as  the  present  stream  furnishes  except  in  times  of 
flood.  The  other  hypothesis  was  suggested  by  Mr.  Blazer  as  his  only  solution  of  a  problem 
on  which  he  had  pondered  for  years.  When  the  canal  was  built,  so  he  surmises,  the  valley 
bottom,  now  half  a  mile  wide,  was  gulHed  out  so  deeply  that  it  could  not  be  cultivated. 
Possibly  an  alluvial  plain  which  had  formerly  been  cultivated  had  been  rapidly  gulhed  by 
the  same  process  which  is  now  beginning  to  destroy  the  present  plains.  At  any  rate  the 
ancient  inhabitants  were  obhged  to  have  recourse  to  the  land  at  the  top  of  the  main  terrace. 
Having  more  skill  than  we  generally  suppose,  they  were  able  to  achieve  the  work  of  making 
the  canal  without  tools  of  iron,  although  the  difl&culties  due  to  the  washing  away  of  sections 
of  it  by  the  sudden  floods  of  little  tributary  gullies  must  have  been  great.  Which  of  these 
two  hypotheses  is  correct  can  not  now  be  determined,  nor  is  it  essential.  In  either  case  it 
seems  probable  that  since  man  occupied  the  country  the  hydrographic  conditions  have 
changed,  a  conclusion  which  agrees  with  the  other  evidence  in  showing  that  at  least  the  last 
cycle  of  the  terrace-making  process  has  occurred  since  man  began  to  build  villages  and 
practise  agriculture. 


HUNTINGTON 


PLATE  2 


A.  Ruins  of  little  stone  terraces  at  Rincon  Canyon.  TKe  stones  have  here  been  much  disturbed  by  occasional  floods. 

less  disturbed,  bushes  hide  them  and  make  photography  diflicult. 

B.  Defensive  Hohokam  walls  on  a  hilltop  near  San  Xavier. 

C.  Looking  down  from  the  top  of  the  Tnnchetas  of  the  Magdalena  River,  showing  terraced  fields  on  the  dry  slope  and 

its  base.  The  rectangle  in  the  center  of  the  terraces  is  the  ceremonial  platform  described  on  page  68. 

D.  Site  of  an  ancient  village  in  Southern  .Arizona,  metate  and  mam  stones  for  grinding  seeds  in  the  foreground. 


In  places  where  they  are 


modern  irrigated  fields  at 


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CHAPTER  VII. 

THE  ANCIENT  PEOPLE  OF  SOUTHERN  ARIZONA. 

We  now  come  to  far  the  most  important  type  of  evidence  as  to  the  relation  of  man  to 
the  climate  of  pre-Columbian  days.  The  number  of  ruins  in  southern  Arizona  and  northern 
Sonora  is  remarkable.  I  do  not  here  refer  to  the  well-known  cliff-dwellings,  nor  to  the 
ancient  villages  and  irrigation  works  of  the  Gila  Valley  and  its  tributaries.  In  addition 
to  these  there  are  literally  hundreds  of  villages  located  still  farther  south.  Most  of  them 
have  never  been  examined  at  all  by  scientists,  and  none  have  been  adequately  described. 
Indeed,  most  people  who  hve  in  their  immediate  vicinity  scarcely  know  of  their  existence. 
The  reason  is  obvious.  Usually  the  ruins  are  so  insignificant  in  appearance  that  an  un¬ 
observant  traveler  might  ride  for  a  mile  through  a  village  without  becoming  aware  of 
the  fact.  (See  Plate  2,  d.)  On  the  hilltops  walls  are  sometimes  found,  built  evidently  for 
protection;  on  the  slopes  below  the  fortresses  little  terraces  for  dwelling-houses  or  other 
purposes  are  located.  These  have  been  duly  noted  by  anthropologists,  as  have  ancient 
pictographs  in  certain  passes  or  near  the  fortresses.  For  our  present  purpose,  however, 
they  are  of  relatively  slight  importance.  The  really  significant  ruins  are  those  of  a  great 
number  of  villages  located  in  the  plains.  Their  sites  are  now  reduced  to  barren  expanses 
strewn  with  ornamented  bits  of  broken  pottery,  fiint  knives  and  arrowheads,  stone  hammers 
and  axes,  mano  and  metate  stones  for  grinding  seeds,  and  in  some  cases  rectangular  lines  of 
boulders  placed  erect  at  intervals  of  a  foot  or  two,  and  evidently  outlining  the  walls  of 
ancient  houses.  Here  and  there  a  little  mound  a  foot  or  two  high  shows  where  a  house 
was  located.  In  almost  every  village  an  oval  hollow  surrounded  by  a  low  wall  covers  an 
area  100  to  200  feet  long  by  half  as  wide — not  a  reservoir,  as  one  at  first  supposes,  but 
probably  a  ceremonial  precinct  of  some  sort.  Aside  from  this  nothing  remains.  Yet 
there  can  be  no  question  that  these  were  once  ancient  villages.  In  many  cases  the  ground 
to  a  depth  of  2  feet  or  more  is  thickly  filled  with  bits  of  pottery,  while  the  surface  is  so 
strewn  with  similar  bits  that  one  can  scarcely  walk  without  stepping  upon  them.  The 
houses  were  probably  built  of  branches,  wattled  perhaps  with  mud.  Such  houses  in  course 
of  time  would  utterly  disappear,  for  the  wood  would  decay,  the  clay  used  for  wattling 
would  partly  blow  away,  and  the  rest  would  be  so  small  in  amount  that  it  would  not  be 
noticeable.  Where  a  house  was  more  thickly  wattled  than  usual  or  was  built  of  adobe  low 
mounds  now  tell  the  tale.  Other  dwellings,  in  villages  close  to  the  mountains  where  stone 
is  easily  available,  were  strengthened  at  the  base  of  the  walls  by  upright  boulders  which 
still  stand  in  their  original  position,  so  that  one  can  see  the  exact  form  of  house  after  house. 
The  majority  of  the  houses,  however,  have  disappeared,  and  in  many  cases  whole  villages 
show  scarcely  a  trace  of  the  original  dwellings.  Yet  they  were  no  transitory  villages. 
The  amount  of  pottery  shows  that  they  must  have  been  filled  with  a  busy  population  for 
centuries.  In  certain  cases,  to  be  sure,  the  amount  is  so  small  as  to  indicate  only  a  brief 
occupancy.  In  the  larger  ruins,  however,  the  amount  is  literally  scores  of  times  as  great 
as  in  modern  Indian  villages  such  as  Cababi  or  Juivak,  whose  inhabitants  still  use  pottery 
almost  entirely,  and  which  have  been  inhabited  for  at  least  50  years.  It  is  equal  to  the 
amount  found  in  Asiatic  ruins  which  are  proved  by  dated  records  to  have  been  inhabited 
for  hundreds  of  years.  The  ancient  villages  are  insignificant  in  appearance,  not  from  any 
lack  of  traces  of  prolonged  human  occupancy,  but  merely  because  of  the  flimsy  construction 
of  the  houses  and  the  length  of  time  since  their  abandonment. 

47 


48 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


ANCIENT  CONDITIONS  OF  LIFE  AMONG  THE  HOHOKAM. 

Before  proceeding  to  discuss  the  ruins  in  detail,  one  or  two  points  of  general  importance 
need  emphasis.  In  the  first  place,  the  builders  of  the  villages  are  not  known  to  have  been 
allied  to  any  tribe  of  modern  Indians.  They  may  possibly  have  been  related  to  such  folk  as 
the  Zuni  or  Moki  tribes,  but  of  this  we  have  as  yet  no  decisive  proof.  Probably  they  were  at 
most  no  nearer  to  them  than  the  primitive  Teuton  was  to  the  modern  Anglo-Saxon,  or  the 
ancient  Jew  to  the  modern  fellah  peasant  of  Palestine.  To  assume  that  because  the 
modern  Indians  follow  certain  practises  the  ancient  inhabitants  also  did  so,  is  as  fallacious 
as  to  assume  that  because  the  modern  people  of  Palestine  beheve  in  the  seclusion  of  women 
the  ancient  Jews  did  likewise — or  that  as  the  modern  Persians  are  noted  for  their  tendency 
to  prevaricate,  Xenophon  and  others  were  wrong  in  praising  the  ancient  Persians  as  speakers 
of  the  truth.  In  so  far  as  the  habits  and  customs  of  a  people  are  directly  determined  by 
physical  environment,  the  ancient  inhabitants  of  Arizona  must  indeed  have  resembled 
those  of  to-day,  except  in  points  where  a  change  of  chmate,  if  such  has  occurred,  would 
alter  the  prevalent  mode  of  fife.  Undoubtedly  Arizona  has  always  been  relatively  dry  and 
agriculture  has  always  been  dependent  upon  irrigation;  nevertheless  the  poverty,  famine, 
pestilence,  war,  depopulation,  and  other  miseries  which  adverse  changes  of  climate  seem 
to  occasion  may  have  given  rise  to  a  large  body  of  habits  and  customs  widely  different 
from  those  of  earlier  times.  Thus  under  favorable  climatic  conditions  peace  may  have 
prevailed,  whereas  a  change  of  climate  may  have  led  the  tribes  of  the  driest  areas  to  adopt 
predatory  habits,  which  in  turn  compelled  the  occupiers  of  the  better  portions  of  the  land 
to  practise  the  arts  of  both  defense  and  offense.  Again  famine  and  scanty  nutrition  due  to 
decrease  in  the  food  supply  may  have  fostered  plagues  and  pestilences  to  such  an  extent 
that  new  customs  arose  as  to  the  burial  of  the  dead,  or  as  to  the  abandonment  of  houses 
in  which  people  had  died.  In  a  score  of  other  ways  the  habits  of  the  past  may  have  been 
different  from  those  of  the  present,  even  in  matters  directly  controlled  by  physical  environ¬ 
ment;  in  other  respects,  such  as  religion,  social  customs,  and  political  organization,  there 
is  still  greater  room  for  diversity. 

I  emphasize  this  point  because  there  is  a  strong  tendency  to  argue  that,  because  the 
modern  Indians  have  a  certain  custom,  their  predecessors  must  have  done  likewise  1,000 
or  2,000  years  ago.  If  it  were  proved  beyond  doubt  that  physical  conditions  were  then  the 
same  as  now,  this  would  be  more  legitimate;  but  while  the  matter  is  open  to  question,  such 
a  method  of  argument  is  unscientific.  It  may,  of  course,  be  true  that  the  people  of  the 
past  were  much  like  those  of  the  present,  but  in  the  present  state  of  knowledge  it  is  wrong 
to  use  any  such  assumption  as  the  basis  of  reasoning.  To  avoid  the  danger  incident  to 
the  association  of  ideas  with  words,  I  shall  not  use  the  term  Indians  or  Amerinds  in  con¬ 
nection  with  the  ancient  inhabitants,  but  shall  call  them  Hohokam.  “The  term  Hohokam, 
‘That  which  has  perished,’  is  used  by  the  Pimas,”  says  Russell,*  “to  designate  the  race 
that  occupied  the  pueblos  that  are  now  rounded  heaps  of  ruins  in  the  Salt  and  Gila  river 
valleys  [50  to  100  miles  north  of  Tucson].  However  ready  the  Pimas  may  have  been  in 
the  past  to  claim  relationship  with  the  Hohokam  or  relate  tales  of  the  supernatural  origin 
of  the  pueblos,  they  now  frankly  admit  that  they  do  not  know  anything  about  the  matter.” 
The  term  Hohokam,  accordingly,  implies  nothing  as  to  the  origin  or  relationship  of  the 
builders  of  the  ancient  villages,  and  therefore  may  appropriately  be  used  in  a  specific 
sense  for  the  vanished  race  of  southern  Arizona  and  the  neighboring  arid  regions. 

Another  point  which  needs  emphasis  is  that  the  Hohokam  were  a  distinctly  agricultural 
people.  The  ruins  are  located  on  the  edge  of  the  lowest  available  gravel  terrace,  just  above 
broad  expanses  of  rich  alluvial  land.  The  only  exceptions  are  in  allu\dal  plains  so  broad 


*  F.  Russell:  The  Pima  Indians.  26th  Ann.  Rept.  Bureau  American  Ethnology,  Washington,  1908,  pp.  23  and  24. 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


49 


that  there  are  no  gravel  terraces  within  a  reasonable  distance.  In  the  part  of  southern 
Arizona  and  northern  Sonora  under  discussion,  I  examined  the  ruins  of  about  twenty-five 
villages.  Not  one  was  located  primarily  in  a  position  favorable  for  easy  defense;  even 
when  sites  suitable  for  this  purpose  were  close  at  hand  they  were  not  utilized  for  the  main 
village,  but  only  in  a  secondary  fashion  as  refuges,  apparently  in  troublesome  times, 
perhaps  toward  the  last  days  of  the  Hohokam.  Water,  also,  to  judge  from  present  con¬ 
ditions,  was  not  a  prime  factor  in  the  choice  of  sites  for  villages.  Fully  haK  of  the  ruins  that 
I  examined  lie  from  0.51  to  8  miles  from  the  nearest  permanent  spring  or  perennial  stream. 
All  the  \'illages  were  obviously  placed  where  it  would  be  most  easy  to  reach  rich  alluvial 
land  capable  of  producing  abundant  crops  if  properly  irrigated.  Fewkes,  Mindeleff,  Hough, 
and  other  anthropologists  who  have  written  on  the  similar  ruins  farther  north  and  east 
all  emphasize  the  peaceful,  agricultural  character  of  the  ancient  inhabitants.  The  mode 
of  life  of  the  Hohokam,  whoever  they  were,  clearly  had  no  resemblance  to  that  of  such 
warlike,  hunting  tribes  as  the  modern  Apaches.  Agriculture  was  almost  their  sole  reliance, 
for  domestic  animals  other  than  the  dog  were  unknown  in  pre-Columbian  North  America. 
Beasts  of  the  chase  were  not  eaten  to  any  great  extent,  as  appears  from  the  scarcity  of  their 
bones  in  the  various  old  pueblos  and  cliff-dwellings  where  ancient  scrap-heaps  have  been 
found  on  the  upper  tributaries  of  the  Gila  and  Salt  rivers  and  elsewhere.  Some  bones, 
to  be  sure,  are  found,  showing  that  the  Hokoham  had  no  aversion  to  flesh,  but  the  number 
is  not  large.  Traces  of  corn  and  beans  and,  to  a  much  less  extent,  of  wild  products  are 
found  in  much  greater  abundance,  showing  that  the  main  source  of  livelihood  was 
agriculture. 

There  is  still  another  point  on  which  stress  should  be  laid  at  the  outset.  In  the  absence 
of  any  proof  to  the  contrary,  we  shall  assume  that  the  Hohokam  were  in  general  the  same 
as  the  rest  of  mankind.  For  instance,  if  we  find  ten  houses  of  ordinary  size  in  a  village, 
we  shall  assume  that  ten  families  lived  there.  This  may  prove  to  be  a  mistake,  but  the 
burden  of  proof  is  on  those  who  assume  that  ten  houses  represent  less  or  more  than  ten 
families.  Likewise  we  shall  assume  that  the  Hohokam  did  not  leave  a  good  location  for  a 
poor  one  except  temporarily  under  stress  of  exceptional  circumstances.  The  writings  of 
anthropologists  are  full  of  assumptions  directly  contrary  to  this.  For  instance,  Mindeleff 
says  that  “A  band  of  500  village-building  Indians  [by  which  he  means  the  people  whom  we 
have  called  Hohokam]  might  leave  the  ruins  of  fifty  villages  in  the  course  of  a  single  cen¬ 
tury.”*  That  is,  he  assumes  a  degree  of  mobility  unparalleled  among  any  modern  agri¬ 
cultural  or  village-building  people.  Possibly  he  is  right,  but  such  an  assumption  can  be 
accepted  only  after  careful  proof.  Accordingly  in  the  following  pages  the  reader  must 
bear  in  mind  that,  when  density  of  population  is  spoken  of,  we  refer  to  the  density  which 
would  have  existed  if  the  Hohokam  had  been  like  other  normal  races  in  the  same  stage  of 
development. 

One  final  point  deserves  to  be  kept  in  mind.  In  comparing  the  capacity  of  the  country 
to  support  population  at  present  with  its  capacity  in  the  past,  allowance  must  be  made 
for  the  fact  that  the  ancient  inhabitants  were  handicapped  by  the  lack  of  many  of  the 
accessories  which  we  deem  most  essential.  Cattle-raising,  the  cultivation  of  wheat,  barley, 
and  oats,  the  use  of  iron  or  metal  tools,  the  industries  connected  with  transportation  by  rail, 
wagon,  horse,  donkey,  or  any  other  means  except  the  backs  of  men  and  dogs,  and  finally 
the  many  activities  connected  with  mining,  were  all  unknown  to  the  Hohokam.  None 
of  these  things  existed  in  the  America  of  their  day.  Not  only  was  the  population  entirely 
agricultural,  but  its  agriculture  was  carried  on  without  any  facilities  except  stone  imple¬ 
ments,  and  plants  such  as  corn  and  beans,  indigenous  to  America. 


*  13th  Annual  Report  of  the  Biu'eau  of  Ethnology,  1891-92,  p.  259. 


50 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


THE  FORMER  POPULATION  OF  THE  SANTA  CRUZ  VALLEY. 

Turning  now  to  the  discussion  of  specific  areas,  it  is  evident  that  the  solution  of  our 
problem  depends  upon  the  relative  density  of  population  and  the  amount  of  water  available 
for  agriculture  in  the  past  as  compared  with  the  present.  We  must  exclude  regions  now 
well  populated,  for  they  prove  nothing  either  one  way  or  the  other.  We  must  also  exclude 
regions  now  depopulated  and  full  of  ruins,  but  capable  of  being  reoccupied.  These  also 
prove  nothing :  the  driving  out  of  the  former  inhabitants  may  have  been  due  to  pestilence, 
or  to  the  incursion  of  warlike  tribes,  such  as  the  Apaches ;  but  the  pestilence  and  the  raids, 
in  their  turn,  may  have  been  the  result  of  adverse  climatic  changes.  Accordingly  we  shall 
pay  little  attention  to  such  regions  and  shall  confine  ourselves  for  the  present  to  the  almost 
uninhabited  lower  part  of  the  Santa  Cruz  Valley  below  Tucson,  and  to  certain  tributary 
valleys  with  an  equally  sparse  population.  Then,  for  the  sake  of  comparison,  we  shall 
consider  the  Altar  and  Magdalena  valleys  in  northern  Sonora.  These,  like  the  Santa  Cruz 
and  its  tributaries,  rise  near  the  border  between  Mexico  and  Arizona,  but  instead  of  flowing 
northwest  for  150  miles  to  the  Gila,  they  flow  a  similar  distance  to  the  southwest,  where 
they  unite  and  empty  into  the  Gulf  of  Cahfornia.  As  a  matter  of  fact,  neither  the  Altar- 
Magdalena  nor  the  Santa  Cruz  sends  any  water  to  the  sea  except  in  occasional  years  of 
phenomenal  floods.  The  permanent  stream  of  the  Santa  Cruz  ends  near  Tucson,  more 
than  70  miles  from  the  Gila,  while  the  permanent  stream  of  the  Altar  terminates  near 
Caborca,  about  50  miles  from  the  Gulf.  (See  map,  frontispiece.) 

Before  investigating  the  ruins,  let  us  see  how  many  people  the  Santa  Cruz  Valley  is 
capable  of  supporting  by  agriculture  at  the  present  time.  According  to  Professor  R.  H. 
Forbes,  the  records  of  the  Arizona  Experiment  Station,  of  which  he  is  the  Director,  show 
that  the  entire  drainage  area  of  the  Santa  Cruz,  including  all  its  tributaries,  contains 
approximately  6,000  acres  under  cultivation  of  some  sort.  This  includes  not  only  areas 
regularly  irrigated  in  the  ordinary  fashion  bj'’  surface  water,  but  also  some  that  depend 
upon  underground  water  raised  by  steam  or  gasoline  pumps,  and  other  considerable  tracts 
which  are  watered  merely  by  temporary  floods  and  hence  produce  only  a  single  crop  of 
alfalfa  per  year  instead  of  four  or  five,  as  is  the  case  in  the  lands  receiving  more  abundant 
water.  Under  the  best  system  of  irrigation  available  at  the  present  time,  Professor  Forbes 
estimates  that  for  every  2  acres  brought  under  full  cultivation  one  person  is  added  to  the 
population  of  Arizona.  This  includes  merchants,  artisans,  and  all  the  varieties  of  people 
needed  to  carry  on  the  business  of  life.  In  other  words,  if  the  Santa  Cruz  Valley  were 
cut  off  from  the  rest  of  the  world  and  left  to  its  own  resources,  as  it  was  in  the  days  of  the 
Hohokam,  the  population  would  be  limited  to  the  number  of  persons  who  could  be  sup¬ 
ported  on  the  6,000  acres  of  irrigated  or  partly  irrigated  land.  To  this  number  nothing 
could  be  added  by  dry  farming  without  irrigation,  for  Professor  Forbes  expressly  states 
that  at  the  present  time,  in  spite  of  various  attempts,  no  such  thing  as  genuine  dry  farming 
is  carried  on  in  the  lower  parts  of  Arizona.  Experiments  are  in  progress  which  may  soon 
render  it  possible,  but  any  such  process  was  certainly  far  beyond  the  capacity  of  primitive 
people  like  the  Hohokam.  A  certain  number  of  persons  might  be  added  by  the  possibilities 
of  hunting  and  of  sustenance  from  wild  products,  such  as  the  fruit  of  the  cacti,  the  mesquite 
beans,  and  so  forth.  The  number  would  be  limited,  however,  for  it  is  well  known  that 
a  hunting  population  of  one  person  to  the  square  mile  is  dense  even  in  a  moist  region 
furnishing  abundant  forage  for  herbivores  and  rodents.  In  a  dry  region  like  Arizona 
the  number  would  be  less.  Nor  could  wild  fruits  and  seeds  add  greatly  to  the  density  of 
population,  for  they  are  abundant  in  the  years  of  good  rainfall  when  the  cultivated  crops 
are  also  abundant,  while  they  fail  in  dry  years,  “especially  in  hard  times,”  as  a  Pima 
Indian  naively  remarked  to  Russell.  In  times  of  poor  crops  the  Hohokam  doubtless 
made  extensive  use  of  wild  products;  but  this  means  that  there  could  not  have  been  any 


THE  KUINS  OF  SOUTHERN  ARIZONA. 


51 


large  number  of  people  dependent  upon  such  products  alone,  for  if  such  were  the  case,  part 
of  the  population  would  inevitably  have  starved  in  dry  years. 

At  the  present  time  the  region  to  the  west  of  the  Santa  Cruz  Valley  is  inhabited  only 
by  Indians.  They  utilize  what  little  water  is  to  be  found  and  carry  on  a  httle  hunting.  A 
large  part  of  their  sustenance,  however,  is  derived  from  the  cattle  and  horses  introduced 
from  Europe.  Besides  this  they  have  deep  wells,  a  convenience  unknown  to  the  Hohokam 
because  of  their  lack  of  iron  tools.  Moreover,  the  modern  Indians  utilize  wheat,  barley, 
and  other  plants  introduced  by  the  Spaniards;  and,  finally,  they  go  out  in  hard  times  to 
work  in  mines  or  in  the  towns  of  the  white  man.  In  spite  of  all  the  advantages  which  the 
modern  Indian  has  over  the  old  Hohokam,  the  population  of  the  Indian  region  west  of  the 
Santa  Cruz  amounts  to  an  average  of  only  one  per  square  mile,  and  could  not  be  increased 
greatly,  if  at  all,  without  the  introduction  of  some  new  means  of  hvelihood.  Take  away 
from  the  modern  Indian  his  cattle,  wells,  wheat,  and  other  results  of  the  white  man’s 
presence,  and  the  population  would  be  cut  in  half.  No  race,  whether  Hohokam  or  Indian, 
could  hope  to  exist  in  any  but  the  scantiest  numbers  without  the  aid  of  irrigation. 

Coming  back  once  more  to  the  amount  of  irrigated  land  and  the  number  of  people 
which  it  could  support,  we  recall  that  6,000  acres  of  good  land  under  full  cultivation  would 
support  approximately  3,000  people  under  present  conditions  of  agriculture.  Primitive 
methods  of  agriculture,  however,  as  Professor  Forbes  puts  it,  without  stock,  wheat,  wells, 
or  any  means  of  raising  water  by  mechanical  power,  such  as  the  steam  pumps  which  run 
night  and  day  on  many  farms,  would  by  no  means  permit  of  one  person  for  every  two  acres. 
Russell  gives  some  figures  (pp.  86-8)  as  to  the  amount  of  land  cultivated  by  the  modern 
Pimas.  According  to  him  each  family  cultivates  from  1  to  5  acres  of  thoroughly  irrigated 
land.  On  the  next  page,  however,  he  says  that  the  individual  holdings  of  each  family 
vary  from  100  to  200  steps  in  width,  according  to  the  size  of  the  family.  He  defines  the 
step  as  5  feet,  which  would  make  the  smallest  plots  6  acres  in  size  and  the  largest  25,  so 
we  are  left  in  doubt  as  to  the  actual  amount  under  cultivation  per  individual.  Moreover, 
if  we  knew  the  amount  of  land  per  individual  among  the  Pimas,  we  should  still  know 
nothing  as  to  the  Hohokam,  for  the  Pimas  get  at  least  half  their  living  from  the  white 
man’s  cattle,  from  government  grants,  from  work  in  the  towns,  and  from  many  sources 
unknown  to  the  Hohokam.  Hence  we  come  back  to  the  figures  of  Professor  Forbes.  If 
the  white  man  with  his  steam  pumps  for  irrigation  and  his  iron  tools  for  digging  canals  and 
making  dams  can  only  cultivate  6,000  acres,  the  Hohokam  could  scarcely  cultivate  more. 
If  the  white  man  with  his  winter  wheat,  his  knowledge  of  fertilizers,  and  his  domestic 
animals  for  plowing  and  for  utilizing  hay,  straw,  and  other  materials  inedible  by  man, 
can  support  only  3,000  people,  or  one  for  every  two  acres,  the  primitive  Hohokam,  even 
though  his  standard  of  living  was  lower  and  he  was  aided  by  game  and  wild  fruits,  could 
scarcely  have  made  the  same  6,000  acres  support  more  than  4,500  people,  or  half  as  many 
again  as  the  white  man’s  limit. 

Granting  that  4,000  or  5,000  is  a  reasonable  maximum  limit  to  the  number  of  Hohokam 
who  could  find  a  living  in  the  Santa  Cruz  Valley  under  present  climatic  conditions,  let  us 
next  see  where  they  would  be  located.  Inasmuch  as  the  location  of  the  ruins  and  the 
consensus  of  opinion  among  ethnologists  prove  that  the  Hohokam  were  preeminently  an 
agricultural  race,  they  must  have  lived  where  both  land  and  water  were  available.  At 
present  about  1,500  of  the  6,000  cultivable  acres  are  at  the  Indian  Reservation  of  San 
Xavier,  9  miles  up  the  Santa  Cruz  to  the  south  of  Tucson;  600  or  700  Indians  now  live 
there,  cultivating  the  land,  raising  cattle,  and  going  out  to  the  neighboring  city  to  work. 
In  the  days  of  the  Hohokam  a  fairly  dense  population  lived  at  San  Xavier,  as  is  proved  by 
various  ruins,  including  a  large  fort  on  the  hilltop  half  a  mile  away  from  the  present  village. 
(See  Plate  2,  b.)  Around  Tucson  itself  lies  another  irrigated  tract  embracing  2,000  or 
more  acres.  We  can  not  tell  exactly  how  extensive  an  area  was  here  occupied  by  the 


52 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Ilohokam,  for  the  houses  and  streets  of  the  present  city  cover  a  large  area.  Just  outside 
the  city,  however,  not  only  to  the  south  nearly  across  the  Santa  Cruz  from  the  old  mission, 
but  also  to  the  north  along  the  terrace  near  the  Southern  Pacific  Railroad,  and  to  the 
west  near  the  Desert  Laboratory  and  the  Hospital,  pottery  and  other  evidences  of  early 
man  are  found  in  abundance,  while  on  Tumamoc  Hill  above  the  Laboratory  the  walls  of 
a  fort  may  be  seen.  Evidently  many  Hohokam  lived  at  Tucson  and  cultivated  the  2,000 
acres  or  more  which  are  there  available  for  irrigation.  A  third  large  tract  of  modern 
cultivation  is  found  along  the  Rillito,  a  stream  which  flows  at  the  southwestern  base  of  the 
Santa  Catalina  Mountains  and  joins  the  Santa  Cruz  about  8  miles  below  Tucson.  Here 
nearly  2,000  acres  are  now  used.  In  the  past  the  Hohokam  evidently  made  use  of  the 
same  land,  for  traces  of  villages  are  found  at  Agua  Caliente,  Tanke  Verde,  and  in  the  angle 
between  the  Rilhto  and  Pantano  washes,  a  mile  southeast  of  Fort  Lowell.  Other  traces 
of  former  occupation  are  found  along  the  terraces  of  the  Rillito,  so  that  there  can  be  little 
question  that  every  available  bit  of  land  was  cultivated. 

The  three  areas  mentioned  above,  namely,  the  San  Xavier  Reservation,  the  vicinity  of 
Tucson,  and  the  Rillito  Valley,  are  the  only  places  where  water  is  now  abundant.  They 
include  about  5,500  of  the  total  6,000  acres  available  for  cultivation.  The  remaining  500, 
more  or  less,  are  scattered  here  and  there  in  small  insignificant  patches.  Thousands  of 
acres  of  most  fertile  soil  lie  along  the  lower  Santa  Cruz  below  Tucson  and  in  many  other 
places,  but  can  not  be  cultivated  for  lack  of  water. 

Let  us  examine  some  of  the  ruins  in  the  region  where  cultivation  is  now  largely  or 
wholly  lacking.  Seven  miles  northwest  of  Tucson  the  little  railroad  section  house  of 
Jaynes  lies  on  the  edge  of  the  alluvial  flats  on  the  northeast  side  of  the  alluvial  plain  of  the 
Santa  Cruz.  From  a  point  a  mile  southeast  of  the  station,  that  is,  toward  Tucson,  pottery 
and  stone  implements  are  strewn  thickly  not  merely  as  far  as  Jaynes,  but  for  nearly  half  a 
mile  beyond.  These  evidences  of  an  ancient  village  lie  upon  a  gravelly  tract  which  now 
rises  perhaps  10  feet  above  the  main  alluvial  plain.  The  width  is  only  about  a  quarter  of 
a  mile  in  most  places,  for  the  village  was  evidently  spread  out  along  the  length  of  the 
stream.  Everywhere  the  pottery  is  so  thick  that  one  walks  on  it  at  almost  every  step. 
The  area  where  pottery  is  thick  amounts  to  at  least  200  acres,  while,  downstream,  potsherds 
are  less  abundantly  strewn  for  about  2  miles  to  a  point  beyond  the  Nine  Mile  Water  Hole, 
near  the  mouth  of  the  Rillito.  In  most  places  the  traces  of  the  ancient  village  are  limited 
to  the  southwest  side  of  the  railroad  toward  the  Santa  Cruz.  Close  to  Jaynes,  however, 
they  cross  over  and  spread  out  upon  a  higher  terrace.  Here  they  cover  the  gravel  '‘mesa,” 
as  the  bahadas  are  locally  called,  and  may  be  seen  in  abundance  along  the  direct  road  from 
Tucson  to  Rillito  just  west  of  the  Flowing  Wells  Ranch,  the  lowest  point  to  which  a 
perennial  water  supply  now  comes.  This  portion  of  the  Jaynes  village  occupied  the 
triangular  point  between  the  Santa  Cruz  and  Rillito  bottom  lands  and  had  an  area  of  at 
least  another  hundred  acres,  while  in  the  outskirts  scattered  fragments  indicate  a  less 
dense  population,  extending  far  on  every  side.  In  this  village  and  in  the  adjacent  main 
area  of  the  Jaynes  ruins  the  pottery  is  so  thick  and  extends  to  such  a  depth  in  the  ground 
that  we  can  scarcely  doubt  that  the  villages  were  densely  populated  for  a  long  time. 

The  number  of  people  contained  in  the  original  villages  can  not  be  estimated  with  any 
exactitude.  An  approximation  may  be  made  from  comparison  with  the  ruins  at  Sabino 
Canyon,  a  tributary  of  the  Rillito.  Where  the  Sabino  brook  flows  southward  out  of  the 
Santa  Catalina  Mountains  it  has  deposited  a  broad  fan  of  gravel,  in  which  it  has  now  cut  a 
wide  flood-plain  bordered  by  a  terrace.  On  the  gravel  terrace  east  of  the  stream,  a  Hoho¬ 
kam  village  was  located.  To-day  the  only  inhabitants  of  the  immediate  vicinity  are 
two  or  three  Mexican  ranchers  who  use  all  the  available  water  to  irrigate  a  score  or  more 
acres  of  bottom  land.  In  the  past  the  village  appears  to  have  been  quite  populous.  In 
the  triangle  between  Sabino  and  Bear  Canyon  “Washes”  an  area  of  35  acres  is  covered  with 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


53 


the  foundations  of  houses,  while  a  surrounding  area  of  the  same  size  is  strewn  with  pottery, 
but  less  thickly  than  the  main  area.  The  Hohokam  of  Sabino,  being  close  to  the  moun¬ 
tains,  employed  stones  to  strengthen  the  foundations  of  many  of  their  houses.  The 
outlines  can  still  be  seen  with  perfect  distinctness,  rectangles  of  boulders  1.5  to  2  feet  in 
long  diameter  set  up  on  end  a  foot  or  two  apart.  My  companion  (Mr.  Bovee)  and  I 
counted  62  houses  in  the  35  acres  of  the  central  area,  and  there  may  have  been  others 
concealed  by  gravel  washed  down  from  the  mountains.  Moreover,  part  of  the  old  houses 
may  have  had  no  stone  foundations.  At  any  rate  the  village  certainly  contained  at  least 
62  houses  of  various  sizes  scattered  at  intervals  of  100  or  200  feet  over  an  area  of  35  acres. 
The  houses  vary  in  size.  Many  small  ones,  located  as  a  rule  on  the  outskirts  of  the  village, 
are  only  about  15  by  20  feet  in  dimensions  and  are  often  divided  into  two  rooms.  The 
ones  nearer  the  center  of  the  village  are  larger,  and  one  inclosure  has  a  size  of  250  feet  by 
110;  another  of  almost  equal  size  appears  to  have  been  a  temple;  it  is  divided  into  several 
rooms  surrounding  a  courtyard,  in  the  midst  of  which  is  located  a  circular  pavement  about 
15  feet  in  diameter.  Judging  by  the  number  of  houses,  the  amount  of  pottery,  and  the 
presence  of  a  temple  or  other  large  public  structure,  this  was  no  temporary  village,  but 
was  inhabited  permanently.  The  inhabitants  must  have  been  cultivators  of  the  soil, 
for  their  village  is  carefully  placed  where  the  stream  comes  out  of  the  mountains  and 
the  arable  land  begins.  Across  Bear  Canyon  Wash  a  minor  village  or  suburb  still  shows 
the  ruins  of  six  houses.  Apparently  at  least  68  famihes  lived  here,  which  would  mean  at 
least  250  people.  Their  support  would  require  500  acres  of  land,  according  to  the  estimates 
of  Professor  Forbes.  There  is  apparently  sufficient  land  in  the  vicinity,  but  only  a  small 
part  of  it  can  now  be  watered.  The  villagers  can  scarcely  have  used  the  lands  or  the  water 
farther  down  the  valley  or  in  other  neighboring  valleys,  for  each  of  these  has  its  own  ruins. 

Leaving  the  matter  of  water  supply,  let  us  attempt  to  form  some  idea  of  the  number 
of  people  who  lived  in  the  old  Jaynes  village.  The  pottery  at  Sabino  is  by  no  means  so 
abundant  as  at  Jaynes,  indicating  that  the  population  was  less  dense.  It  also  seems  to 
extend  to  a  less  depth  in  the  ground,  suggesting  a  less  long  occupation ;  yet  there  is  enough 
to  indicate  an  occupation  of  centuries,  if  comparison  with  modern  Indian  villages  is  any 
guide.  However  this  may  be,  it  seems  clear  that  the  great  double  village  near  Jaynes  was 
more  thickly  populated  than  Sabino.  If  the  300  or  more  acres,  which  were  densely  strewn 
with  pottery,  were  covered  with  houses  placed  no  more  closely  than  those  of  Sabino,  that 
is,  at  average  intervals  of  140  feet,  the  total  number  must  have  been  at  least  500,  without 
taking  account  of  the  large  number  which  clearly  existed  in  the  surrounding,  less  densely 
populated  areas.  This  would  mean  at  least  2,000  people  in  the  main  town  and  certainly 
500  in  the  suburbs.  These  2,500  would  need  at  least  5,000  acres  of  irrigable  land,  according 
to  the  best  authority  on  modern  agriculture  in  Arizona.  In  other  words,  we  have  seen  that 
in  the  vicinity  of  the  sites  where  agriculture  is  now  most  feasible  something  like  5,500  acres 
of  land  are  in  use.  Ruins  indicate  that  all  of  this  was  cultivated  in  the  days  of  the  Hoho¬ 
kam,  and  common  sense  tells  us  that  no  sane  man  would  leave  the  easily  watered  land 
uncultivated  and  betake  himself  to  land  with  a  precarious  water-supply.  Nevertheless, 
in  the  region  just  below  the  Tucson  area  of  cultivation  the  Hohokam  established  a  great 
village  which  must  have  demanded  almost  as  much  land  as  the  entire  amount  now  in  culti¬ 
vation.  All  the  land  available  for  their  use  was  in  a  district  below,  that  is,  downstream 
from  the  last  extensive  area  which  now  is  capable  of  profitable  cultivation.  Its  case  is 
exactly  like  that  of  the  Sabino  ruins.  Both  appear  to  have  been  permanent  agricultural 
villages,  but  both  demand  an  amount  of  irrigable  land  far  in  excess  of  that  now  available. 

Ruins  of  the  Jaynes  type  are  numerous.  One  of  the  most  important  is  located  at  the 
so-called  “Point  of  the  Tucson  Mountains,”  or  Charco  del  Yuma,  as  the  Mexicans  call  it, 
a  mile  or  more  south  of  Rillito  Station  on  the  Southern  Pacific  Railroad.  The  name  is 
commonly  abbreviated  to  Charco  Yuma,  and  has  sometimes  been  incorrectly  printed  as 


54 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Shakaynma.  Here,  below  the  mouth  of  the  Rillito  Wash,  the  broad,  waste-filled  basin  of 
the  combined  Rillito  and  Santa  Cruz  streams  contracts  to  a  narrow  neck.  On  the  south 
the  volcanic  range  of  the  Tucson  Mountains  projects  into  the  plain,  while  about  2  miles 
to  the  north  the  rocky  foothills  of  the  granite  range  of  the  Tortillitas  rise  from  the  alluvial 
gravel.  A  buried  dam  of  rock,  so  to  speak,  here  crosses  the  Santa  Cruz  Valley  beneath 
the  cover  of  alluvial  deposits,  causing  the  level  of  underground  water  to  be  relatively  high 
upstream  from  the  point  of  the  mountains,  while  downstream  it  rapidly  falls.  In  the  spring 
of  1910  we  found  that  the  source  of  surface  water  nearest  to  Charco  Yuma  was  8  miles  up 
the  Santa  Cruz  at  the  Nine  Mile  Water  Hole;  there  the  amount  was  sufficient  for  drinking 
purposes,  but  not  for  any  appreciable  irrigation.  Ranchers  engaged  in  raising  cattle 
informed  us  that  no  water  whatever  had  come  down  the  river  during  the  preceding  winter, 
although  during  the  summer  of  1909,  when  the  rainfall  amounted  to  almost  exactly  the 
average  quantity  of  7  inches,  floods  came  down  after  15  to  20  showers.  In  some  cases 
the  flow  continued  only  2  hours;  in  the  height  of  the  rainy  season,  however,  a  brook  of 
greater  or  less  size  flowed  steadily  for  2  weeks.  The  average  duration  of  the  floods  was 
about  36  hours.  From  this  we  infer  that,  during  a  summer  of  average  rainfall,  surface 
water  flows  as  far  as  Charco  Yuma  for  about  30  days,  during  July  or  August.  Socoro 
Ruelas,  a  Mexican  who  in  boyhood  and  early  manhood  lived  at  the  old  stage  station,  one 
of  the  cattle  ranches  at  the  Point  of  the  Mountains,  states  that  in  vunter  water  seldom 
flows  there.  Even  the  heavy  showers  of  summer  sometimes  fail  to  send  any  stream  so 
far  down  the  valley.  The  nearest  permanent  source  of  water,  as  has  been  said,  is  at  the 
Nine  Mile  Water  Hole,  8  miles  away,  but  even  this,  he  says,  sometimes  dries  up,  although 
at  other  times  (such  as  the  late  seventies  or  early  eighties)  water  flows  2  or  3  miles  from 
it  and  has  actually  been  used  for  irrigation.  From  the  spring  of  1885  to  August  1887, 
according  to  the  Mexican,  no  water  whatever  came  down  as  far  as  the  Point  of  the  Moun¬ 
tains.  In  1884,  when  Ruelas’s  father  dug  his  well,  water  was  struck  at  a  depth  of  28 
feet;  during  the  following  dry  years  the  level  fell  below  this,  but  water  never  absolutely 
failed.  In  the  winter  of  1909-10  the  level  was  22  feet,  I  can  not  vouch  for  the  dates 
here  given,  but  there  can  be  no  question  as  to  the  general  accuracy  of  the  facts. 

A  talk  with  Mr.  Langhorn,  the  station-master  at  RilHto,  a  mile  or  more  north  of  the 
old  stage  station  and  the  Hohokam  village,  seems  at  first  sight  to  put  quite  a  different 
aspect  on  the  matter.  Here  a  narrow  strip  of  cultivated  land  extends  along  the  railroad 
for  more  than  3  miles.  “Talk  about  dry  farming,’'  said  Mr.  Langhorn,  “it’s  the  easiest 
sort  of  thing.  Five  inches  of  rain  a  year  is  all  we  need  here.  Just  look  at  my  fields.  They’re 
not  so  good  as  usual,  but  they  show  what  can  be  done  even  in  a  bad  year  like  this.  It’s 
all  in  the  way  you  plow  and  harrow  and  roll.”  A  little  investigation,  however,  soon 
shows  that  the  300  acres  here  cultivated  are  provided  with  very  effective  irrigation,  not 
artificial,  but  natural.  Because  of  the  raising  of  the  level  of  ground  water  in  this  particular 
spot  by  the  contraction  of  the  valley,  the  moisture  is  nearer  to  the  surface  than  elsewhere. 
When  floods  come  down,  water  accumulates  in  pools.  Mr.  Langhorn  pointed  out  patches 
in  which  the  barley  was  then  particularly  fine,  but  which  can  not  be  planted  in  some  years 
because  of  the  moisture.  Even  in  bad  seasons  these  fields  are  much  wetter  than  any  other 
place  for  many  miles.  The  winter  of  1909-10  was  by  no  means  propitious.  Although  the 
rainfall  amounted  to  only  a  little  less  than  the  average,  it  was  badly  distributed,  most  of 
it  falling  early  in  the  winter.  Accordingly  the  grain  planted  in  September  and  October, 
and  even  in  early  November,  grew  fairly  well,  while  that  planted  after  the  middle  of  No¬ 
vember  failed  to  head.  Even  in  the  best  part  of  the  300  acres  available  for  cultivation 
in  this  district,  the  hay  crop,  for  which  the  barley  is  planted,  was  expected  to  amount  to 
only  about  15  tons,  although  in  the  preceding  year  it  had  been  95.  This  particular  area 
has  not  been  cultivated  long,  and  its  possibilities  in  really  dry  seasons  have  not  been  tested. 
At  least  a  quarter  and  possibly  a  third  of  the  winters  in  the  last  43  years  have  been 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


55 


even  more  unpropitious  that  was  1909-10.  If  a  rainfall  of  2.88  inches  in  that  year  could 
cause  the  diminution  of  the  crop  to  the  extent  of  five-sixths,  it  requires  no  demonstration 
to  show  that  the  fields  must  have  been  almost  useless  in  the  9  years,  since  1867,  when 
the  winter  rainfall  has  been  less  than  that  amount.  Many  attempts  have  been  made 
to  cultivate  areas  outside  the  300  acres  now  in  use,  but  have  met  with  no  success.  Of  course 
in  years  like  1904-05,  with  nearly  15  inches  of  winter  rain  and  6  in  the  summer,  or  1906-07, 
with  nearly  8  in  the  winter  and  11  in  the  summer,  fine  crops  can  be  raised  in  a  great  many 
places;  but  this  is  the  exception,  not  the  rule. 

To  sum  up  the  conditions  at  Charco  Yuma  as  set  forth  by  the  two  men  quoted 
above  and  by  others,  it  appears  that  no  permanent  supply  of  water  is  available  without 
the  digging  of  wells  at  least  25  feet  deep.  The  nearest  permanent  supply  of  surface  water 
is  8  miles  away.  A  period  of  two  full  years  may  elapse  without  a  single  temporary  flow  of 
water.  The  total  amount  of  land  capable  of  cultivation  amounts  to  about  300  acres,  or 
enough  for  150  people,  but  this  yields  very  variable  crops,  falling  off  as  much  as  85  per  cent, 
even  in  years  which  are  by  no  means  the  worst.  We  are  almost  certain  that  the  ancient 
Hohokam  knew  nothing  of  wells,  for  not  only  have  none  ever  been  described  among  their 
ruins,  but  the  total  absence  of  iron  implements  would  render  the  digging  of  deep  wells 
practically  impossible.  Moreover,  the  Hohokam  had  no  winter  crops  of  any  importance, 
for  the  indigenous  grains  and  food  plants  of  America  do  not  lend  themselves  to  winter 
growth.  Hence  the  ancient  inhabitants  were  limited  to  the  products  of  the  summer 
rains.  Now,  according  to  Ruelas,  no  flood  water  reached  Charco  Yuma  in  1885,  when  the 
summer  rain  amounted  to  3.01  inches,  the  minimum  on  record,  nor  in  1886,  when  it 
amounted  to  4.27.  We  may  safely  say  that  if  no  water  reached  the  place  with  a  fall  of  4.27 
inches,  crops  of  any  appreciable  value  could  scarcely  be  raised  with  less  than  5  inches. 
During  the  45  years  for  which  records  are  available,  15  summers,  or  one-third,  have  had  a 
rainfall  of  less  than  5  inches.  Hence  we  seem  compelled  to  conclude  that  under  Hohokam 
methods  of  agriculture  the  total  amount  of  land  now  available  for  cultivation  amounts  to 
only  300  acres,  which  would  yield  no  appreciable  crop  at  least  one  year  out  of  three. 

The  Hohokam  hved  in  this  vicinity  in  large  numbers.  In  the  fields  around  Rillito 
Station,  according  to  Mr.  Langhorn,  the  plow  frequently  turns  up  bits  of  pottery  or  stone 
implements  from  beneath  5  or  6  inches  of  fine  silt  deposited  by  recent  floods  of  the  Santa 
Cruz.  Half-way  from  the  station  to  the  Point  of  the  Mountains  a  gravelly  tract  of  older 
alluvium  in  the  midst  of  the  silty  areas  of  later  deposition  is  also  well  strewn  with  pottery. 
These  evidences  of  the  presence  of  the  Hohokam  suggest  a  somewhat  numerous  population 
scattered  wherever  alluvial  land  occurs.  No  special  stress,  however,  should  be  laid  upon 
these  facts.  They  are  unimportant  compared  with  the  phenomena  of  Charco  Yuma  proper. 

Where  the  Tucson  Mountains  jut  their  last  spur  forward  toward  the  north,  the  sandy 
bed  of  the  dry  Santa  Cruz  runs  nearly  westward  at  the  base  of  a  series  of  rugged  black 
hills,  rising  from  300  to  500  feet  above  the  plain.  East  of  the  hills,  in  the  narrow  strip  of 
plain  between  their  base  and  the  river-bed,  Mr.  Herbert  Brown,  editor  of  the  Tucson 
Star,  showed  us  the  remains  of  a  large  village,  For  nearly  2  miles  we  found  pottery  and 
other  artifacts  scattered  along  the  base  of  the  mountains,  not  thick  as  a  rule,  but  at  frequent 
intervals,  as  if  houses  had  been  located  here  and  there  along  the  edge  of  the  cultivated 
land,  just  as  they  seem  to  have  been  along  the  Canada  del  Oro  and  other  dry  stream-beds, 
or  as  the  houses  of  the  modern  Indians  are  to-day  at  San  Xavier.  In  the  center  of  the 
village  the  pottery  is  thicker.  Here  we  found  a  great  boulder  of  andesitic  lava  almost 
buried  in  alluvium,  and  studded  with  24  round  holes  about  10  inches  deep  and  3  inches 
in  diameter.  A  similar  block  not  far  away  contains  7  holes  of  the  same  sort.  Long  ago 
the  Hohokam  women  must  have  gathered  here  with  their  stone  pestles,  and  gossiped  as 
they  sat  on  the  great  rocks  and  pounded  the  corn,  beans,  or  other  seeds  to  make  flour  for 
the  daily  bread  of  their  primitive  husbands  and  sons.  Not  far  away  an  elliptical  inclosure, 


56 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


210  by  90  feet  in  size,  is  surrounded  by  thick  mud  walls  which,  in  spite  of  being  much 
broken  down,  still  present  the  appearance  of  a  ridge  4  or  5  feet  high.  The  interior  was 
evidently  hollowed  out  to  a  level  slightly  below  that  of  the  surrounding  plain,  while  the 
walls  of  dry  mud  must  have  had  a  height  of  not  less  than  6  or  8  feet.  Similar  inclosures  are 
found  in  many  ruins,  for  instance  at  Jaynes  on  the  upper  terrace,  where  several  lie  close  to 
the  road  on  the  south  side  just  east  of  where  it  descends  to  the  lower  level  on  which  the 
railway  station  is  located.  Hasty  examination  suggests  that  these  are  reservoirs,  but  a 
little  study  shows  that  usually  they  are  so  located  that  water  could  not  possibly  be  caused 
to  flow  into  them  and  fill  them.  Their  walls  rise  so  far  above  the  level  of  the  plain  that 
even  if  canals,  of  which  there  is  no  sign,  carried  water  to  them,  only  the  lower  portion, 
to  a  depth  of  2  or  3  feet,  could  be  filled.  Moreover,  some  of  them  have  broad  entrances 
not  appropriate  to  reservoirs.  Structures  of  the  same  sort  are  found  in  all  parts  of  the 
drainage  area  of  the  upper  Salt  and  Gila  rivers,  and  go  far  toward  proving  community  of 
race  or  at  least  of  civilization  among  all  the  inhabitants.  Mindeleff  and  others  have  come 
to  the  conclusion  that  these  were  ceremonial  chambers,  roofed,  perhaps,  with  branches 
supported  upon  poles.  This  seems  highly  probable.  If  the  theory  is  correct  the  presence 
of  such  temples  would  in  itself  indicate  the  existence  of  villages  of  considerable  size  and 
permanency. 

Back  of  the  temple  and  the  great  grinding  stones,  if  these  terms  are  allowable,  the 
whole  eastern  and  northern  face  of  the  hills  is  covered  with  low  walls,  2  or  3  feet  high,  pro¬ 
tecting  the  exposed  side  of  roughly  smoothed  spaces  from  10  to  30  feet  wide.  Apparently 
these  were  built  as  places  of  refuge  for  the  inhabitants  of  the  village  below.  Each  one  may 
have  been  covered  with  a  booth  of  branches,  although  there  is  no  direct  evidence  of  this. 
The  Hohokam  certainly  spent  a  good  deal  of  time  here,  for  pottery  is  scattered  thickly. 
Probably  the  potsherds  represent  largely  the  broken  fragments  of  jars  in  which  water  was 
brought  from  below,  although  where  the  water  came  from  is  a  puzzle.  If  the  oval  hollows 
are  temples,  no  sign  of  reservoirs  has  been  detected  anywhere  on  the  plains,  nor  has  any 
trace  of  cisterns  been  noted  on  the  hillsides.  The  number  of  platforms  or  inclosures  is 
great.  At  first  one  is  tempted  to  say  there  must  be  a  thousand  of  them.  We  did  not  count, 
but  a  rough  estimate  shows  that  they  surely  number  several  hundred.  No  distinctly  defen¬ 
sive  walls  are  found  here,  like  those  at  Tumamoc  Hill  near  Tucson  or  on  the  mesa  at  San 
Xavier.  Possibly  this  site  was  abandoned  before  the  pressure  of  hostile  tribes  had  led  to 
the  development  of  the  art  of  defense  to  the  point  where  regular  forts  were  constructed. 
At  any  rate,  the  hill  was  apparently  a  refuge  for  the  inhabitants  of  the  village  on  the  plain, 
and  the  number  of  platforms  agrees  with  the  size  of  the  area  where  pottery  is  found  in 
indicating  a  population  numbered  by  hundreds  of  families. 

On  the  west  side  of  the  hills  forming  the  Point  of  the  Tucson  Mountains  another  large 
village  is  found.  For  a  distance  of  nearly  1.5  miles  along  the  terrace  above  the  alluvial 
plain  of  the  Santa  Cruz,  pottery  and  the  usual  accompanying  artifacts  are  thickly  scattered. 
The  central  portion  of  the  village  occupies  an  area  of  about  200  acres,  while  the  surrounding 
part,  where  the  population  was  less  dense,  covers  a  slightly  larger  additional  area.  In 
the  center  of  the  village  pottery  is  very  thick  and  the  upper  layers  of  earth  are  full  of  it 
to  a  depth  of  2  feet.  In  the  portion  where  pottery  is  thickest,  not  far  from  the  foot  of  the 
hills  on  the  east  and  from  the  terrace  leading  down  to  the  river  on  the  north,  lines  of  stones 
indicate  the  foundations  of  houses,  as  at  Sabino.  We  did  not  count  them,  not  realizing 
at  the  time  how  important  they  might  be.  It  almost  seems  as  if  they  represented  an  occupa¬ 
tion  later  than  that  of  the  rest  of  the  village,  but  this  is  mere  conjecture.  The  decora¬ 
tions  on  the  pottery  and  the  occurrence  of  inclosures  such  as  those  which  we  have  taken 
to  be  temples  prove  that  in  general  the  people  here  were  like  those  in  the  other  villages 
of  this  region.  The  hills  on  this  side  rise  as  steeply  as  on  the  other  and  offer  as  good  a  shelter 
from  enemies,  but  they  seem  to  be  devoid  of  refuges  or  walled  inclosures  like  those  on  the 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


57 


opposite  side.  If  Charco  Yuma  West  of  the  Mountains  had  existed  at  the  same  time  as 
Charco  Yuma  East  of  the  Mountains,  the  same  necessity  for  protection  must  have  existed 
in  both  cases.  Hence  it  seems  probable  that  the  western  and  larger  village  was  abandoned 
in  favor  of  the  eastern  at  a  time  when  protection  against  enemies  had  not  yet  become  a 
vital  necessity.  The  western  village  is  more  favorably  located  than  is  the  eastern  with 
respect  to  agricultural  lands,  such  as  those  of  Rillito  or  the  rest  of  the  Santa  Cruz  Plain, 
but  it  is  not  so  sheltered  as  the  other,  nor  so  near  to  the  river  bed,  whence  water  was  pre¬ 
sumably  derived.  If  a  progressive  diminution  of  the  water-supply  had  anything  to  do 
with  the  matter,  the  supply  of  the  lower  village  would  fail  before  that  of  the  other;  for 
the  village  east  of  the  mountains  is  located  where  the  level  of  permanent  underground  water 
is  at  a  depth  of  a  little  over  20  feet,  and  a  slight  rise  would  bring  it  within  reach  of  the 
surface;  while  in  the  bed  of  the  river  adjacent  to  the  western  village  the  ground-water 
level  is  at  a  depth  of  50  feet  or  more.  The  greater  abundance  of  pottery  in  the  western 
village,  the  greater  depth  to  which  it  is  buried,  the  greater  degree  of  weathering  of  the 
wall  of  the  temple  inclosm’e,  and  the  absence  of  all  defensive  structures  on  the  hills  suggest 
that  the  western  village  dates  from  an  early  time,  presumably  of  peace  and  prosperity, 
while  the  eastern  village  dates  from  a  later  period  of  greater  stress  and  danger.  If  the 
same  line  of  reasoning  is  pursued  farther,  we  may  infer  that  the  absence  of  a  genuine  fort 
at  Charco  Yuma  and  the  presence  of  such  structures  at  Tucson  and  San  Xavier  indicate 
that  in  course  of  time  conditions  grew  still  worse,  so  that  the  outlying  town  at  the  Point 
of  the  Mountains  was  abandoned,  while  the  upper  towns  began  to  seek  the  protection  of 
regular  forts.  The  abandonment  of  the  lower  town  may  have  been  due  to  desiccation  and 
the  consequent  failure  of  the  crops,  or  to  the  growth  of  warlike  tendencies  among  the 
neighboring  peoples. 

In  offering  these  suggestions  we  are  venturing  upon  the  realm  of  theory  rather  than  of 
proven  fact.  The  justification  for  this  lies  in  the  fact  that  among  Asiatic  ruins  of  similar 
character,  in  the  deserts  of  Chinese  Turkestan  and  elsewhere,  written  records  prove  that 
the  villages  were  abandoned  one  after  another,  beginning  far  downstream  and  progressing 
upward.  Further  comment  on  Charco  Yuma  is  unnecessary.  Its  population  was  appar¬ 
ently  almost  as  great  as  that  of  Jaynes;  it  was  inhabited  for  a  long  time,  and  its  people 
must  have  required  much  water  both  for  drinking  purposes  and  for  the  irrigation  of  fields. 
The  supply  available  in  the  vicinity  to-day  is  hmited  to  floods  in  wet  seasons  and  is  often 
entirely  lacking  for  many  months,  sometimes  for  over  2  years  at  a  stretch.  No  trace  of 
reservoirs  has  been  found,  and  no  reservoir  which  could  be  built  in  this  flat,  dry  region  could 
retain  water  more  than  5  or  6  months,  as  is  proved  by  modern  experience  in  more  favored 
locahties.  The  arable  land  is  hmited  to  300  acres,  and  even  this  small  tract  often  fails  to 
produce  a  good  crop. 

Seven  miles  below  Charco  Yuma,  or  24  miles  down  the  Santa  Cruz  from  Tucson, 
Mr.  W.  J.  Wakefield  showed  us  a  smaU  ruin  located  about  0.7  mile  due  north  of  Nelson’s 
Desert  Ranch.  It  is  over  3  miles  from  the  dry  bed  of  the  Santa  Cruz,  and  3  miles  from 
the  lower  end  of  the  strip  of  arable  land  which  begins  at  Rilhto  Station.  The  level  of 
ground  water  is  so  low  that  in  digging  a  well  at  the  ranch  it  was  necessary  to  go  down 
182  feet.  This  is  stated  on  the  authority  of  Mr.  Wakefield,  who  lived  here  as  a  boy 
and  whose  knowledge  of  this  region  and  others,  both  in  Aiizona  and  Mexico,  was  most 
kindly  put  at  our  disposal  at  much  inconvenience  to  himself.  At  the  ruins  near  Nelson’s 
Ranch  the  water-level  must  be  still  lower  than  at  the  ranch.  A  few  small  “washes” 
lead  occasional  floods  down  from  the  Tortollitas  Mountains  some  miles  to  the  north,  but 
there  is  absolutely  no  hint  of  any  permanent  water-supply.  The  ruins  consist  of  a  rec¬ 
tangular  inclosm’e,  210  by  175  feet,  with  the  long  side  running  N.  25  E.  magnetic,  or  N. 
37  E.  true.  A  wall  of  earth,  now  almost  obliterated,  surrounded  the  inclosure  and  was 
pierced  at  the  southern  corner  by  a  gateway.  In  the  opposite,  or  northern,  corner  a 


58 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


mound  or  platform  65  by  50  feet  in  size  rises  8  or  10  feet.  Nothing  like  this  was  found 
in  any  other  ruin  which  I  saw  in  either  Arizona  or  Mexico.  The  pottery  also  was  unusual. 
The  majority  was  of  the  common  type,  terra-cotta  with  brown  lines  forming  triangles, 
feathers,  or  other  patterns.  Certain  pieces,  however,  were  of  large  size,  bright  red  in  color, 
with  black  designs.  These  looked  comparatively  fresh,  as  if  of  late  date,  but  the  appear¬ 
ance  may  have  been  deceptive.  Other  pieces  were  pinkish-purple  in  tint  with  designs  in 
white  lines,  or  else  dark  brown  with  purple  designs.  These,  to  one  who  knows  nothing 
of  pottery,  appear  to  be  older  than  the  ordinary,  more  commonplace  ware.  Some  of  them 
were  ornamented  on  both  sides,  a  practise  not  noticed  elsewhere.  Certainly  the  shape  of 
the  ruins  separates  them  from  others  in  this  part  of  Arizona,  and  the  unusual  variety  of 
design  and  color  in  the  pottery  and  its  uncommonly  fine  texture  suggest  a  higher  artistic 
development  than  is  found  elsewhere.  Also  the  site  is  more  absolutely  waterless  than 
any  other  yet  discovered.  Whether  all  these  things  indicate  great  age  and  early  abandon¬ 
ment  I  do  not  know.  The  village  was  never  large.  Outside  the  rectangular  inclosure 
pottery  extends  thickly  for  only  600  feet,  although  scattered  bits  are  found  for  half  a  mile. 
The  village  was  apparently  agricultural,  although  no  cultivation  is  now  possible  in  its 
vicinity. 

The  list  of  ruins  in  the  lower  Santa  Cruz  Valley  is  not  yet  complete.  Over  50  miles 
from  Tucson,  in  township  8  S.,  Range  7  E.,  near  the  corner  of  sections  20,  21,  and  28,  Mr.  J. 
B.  Wright,  irrigation  engineer  of  the  Santa  Cruz  Reservoir  Company,  showed  us  another 
old  ruin,  about  3  miles  southeast  by  east  of  Santa  Cruz  post-ofiice,  west  of  Toltec  Station. 
Some  day  the  extensive  projects  of  the  reservoir  company  may  possibly  bring  this  region 
under  irrigation,  but  in  1910  no  water  had  been  secured  in  spite  of  a  large  expenditure  of 
money  on  a  dam  and  canals,  and  the  next  year  the  company  gave  up  its  work.  To-day 
the  ruins  are  stOl  miles  away  from  any  region  where  agriculture  is  possible  and  from  any 
source  of  water,  either  for  irrigation  or  drinking.  The  center  of  the  village  is  marked  by 
an  elliptical  inclosme  of  the  usual  type,  which  could  not  possibly  have  been  a  reservoir, 
as  it  stands  too  high.  Pottery  extends  to  a  distance  of  500  to  600  feet  about  it.  Twelve 
miles  south  of  Toltec  Station,  in  an  equally  waterless  district  at  the  northern  base  of  the 
Sawtooth  Mountains,  the  reservoir  company  in  1910  erected  a  large  dam,  now  abandoned, 
which  was  designed  ultimately  to  be  about  40  feet  high,  and  to  hold  in  reserve  a  supposedly 
large  body  of  flood  water  which,  however,  failed  absolutely  to  materialize  in  1910.  At 
the  eastern  end  of  the  dam  we  rode  three-fourths  of  a  mile  through  ancient  pottery.  At 
the  western  end,  a  mile  away,  the  traces  of  a  large  village  can  be  seen.  During  the  progress 
of  the  work  on  the  dam  various  objects  were  brought  to  light,  such  as  an  image  of  a  man, 
another  of  a  pregnant  woman,  a  stone  phallus,  and  some  pieces  of  slate,  very  smooth,  and 
covered  with  carvings  said  to  suggest  hieroglyphics.  These  are  now  in  the  possession  of 
Colonel  Green,  of  Cananea,  Mexico.  In  other  portions  of  the  now  desert  plain  of  the 
lower  Santa  Cruz,  far  below  the  limits  of  any  but  the  largest  floods,  the  workmen  came 
upon  numerous  traces  of  old  villages.  In  one  case,  about  3  miles  southwest  of  Toltec 
Station,  or  half-way  from  Santa  Cruz  post-office  to  the  station,  Mr.  Wright  came  across 
a  drainage  line  which  runs  nearly  east  and  west  across,  instead  of  with,  the  line  of  steepest 
slope.  Such  a  channel  could  scarcely  be  formed  by  nature,  and  hence  Mr.  Wright  thinks 
that  it  may  be  an  ancient  canal,  possibly  the  continuation  of  the  one  which  presumably 
led  to  the  ruin  described  at  the  beginning  of  this  paragraph.  It  is  still  possible  that  the 
construction  of  huge  irrigation  works  such  as  those  projected  by  the  Santa  Cruz  Reservoir 
Company,  with  dams  miles  in  length  and  reservoirs  covering  whole  townships,  may  gather 
sufficient  flood  water  to  cause  the  region  once  more  to  be  populated,  but  no  traces  of  the 
existence  of  any  such  thing  in  the  past  have  ever  been  found.  In  the  Salt  and  Gila  valleys, 
to  be  sure,  old  canals  are  frequently  noted,  but  nothing  at  all  comparable  to  the  works  which 
would  here  be  required.  Hence  there  is  scarcely  the  remotest  possibility  that  they  ever 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


59 


existed.  Without  them  the  only  means  of  sustenance  in  all  the  region  from  Rillito  down¬ 
ward  is  the  hunting  of  jack-rabbits  or  the  keeping  of  cattle  watered  from  deep  wells.  In 
one  or  two  places  a  few  acres  can  at  times  be  cultivated  when  the  floods  come  down  strongly, 
but  any  reliance  upon  agriculture  is  out  of  the  question.  At  best  the  population  is  limited 
to  a  few  cattle  ranches  miles  apart.  Yet  in  the  past  it  was  dotted  with  numerous  agri¬ 
cultural  villages. 

Before  leaving  the  Santa  Cruz  drainage  area  we  must  describe  two  more  sites  located 
close  to  the  mountains  and  affording  phenomena  different  from  anything  yet  discussed. 
The  first  is  at  Gibbon’s  Ranch,  a  mile  or  two  east  of  Sabino  Canyon,  at  the  southern 
base  of  the  Santa  Catalina  Mountains.  The  peculiarity  of  this  site  is  that  it  is  one  of  the 
few  where  the  water-supply  depends  upon  a  spring  rather  than  a  stream.  At  present  the 
site  is  unoccupied.  A  decaying  adobe  house  stands  beside  a  small  reservoir  supplied  by 
two  or  three  trickling  little  springs.  The  total  amount  of  water  at  the  time  of  our  visit 
in  March  1910  would  scarcely  suffice  to  irrigate  3  or  4  acres.  Just  what  its  capacity  is 
can  not  be  stated,  but  at  any  rate  the  owner  of  the  ranch  did  not  find  it  worth  while  to 
practise  agriculture,  and  turned  his  attention  entirely  to  cattle  raising.  Since  his  death  or 
removal,  no  one  has  lived  there.  Some  day,  perhaps,  some  thrifty  Chinese  peasants  will 
establish  here  a  little  market  garden.  They  will  certainly  be  most  skilful  if  they  can  make 
the  water  suffice  for  the  support  of  much  more  than  two  or  three  families.  East  of  the 
spring  a  dry  wash  occasionally  carries  floods  from  the  mountains.  Close  beyond  it  lies 
the  site  of  an  old  village  of  the  same  type  as  the  one  at  Sabino  Canyon.  Mr.  Bovee  and  I 
counted  the  foundations  of  28  houses  in  an  area  of  8  acres.  The  entire  village,  that  is,  the 
district  strewn  with  pottery,  amounts  to  almost  40  acres.  Apparently  the  trickling  springs, 
which  are  not  now  deemed  worth  using,  once  supported  more  than  a  hundred  people. 

At  Gibbon’s  Ranch,  as  in  other  ruins,  a  structure  which  appears  to  have  been  a  temple 
lies  in  the  heart  of  the  village.  Although  in  an  extreme  state  of  ruin,  it  appears  to  have 
been  elliptical  in  shape.  The  main  northern  wall,  which  is  the  best  preserved,  is  about 
105  feet  long  and  is  oriented  east  and  west  magnetic  or  N.  78°  W.  This  brings  up  an 
interesting  fact :  In  all  the  villages  where  stone  foundations  occur  there  seems  to  be  a  more 
or  less  definite  scheme  of  orientation,  which  is  closely  adhered  to  in  the  temples  and  larger 
buildings,  and  is  less  and  less  closely  observed  as  the  structures  decrease  in  size  or  are 
located  at  a  greater  distance  from  the  temple.  I  measured  the  orientation  of  55  foundations 
in  7  different  villages  located  in  four  widely  separated  localities.  They  were  distributed 
as  follows : 

Group  I.  Sabino,  37  measurements;  Bear  Canyon,  3;  Gibbon’s  Ranch,  3. 

Group  II.  Rincon  Valley  near  Sentinel  Butte,  2;  1.5  miles  from  Sentinel  Butte,  8. 

Group  III.  Empire  Ranch,  1. 

Group  IV.  The  Great  Trinchera  of  the  Magdalena  Valley  in  Sonora,  1. 

Out  of  the  55  structures,  only  8,  5  of  which  are  in  the  main  village  in  the  Rincon  Valley, 
diverge  more  than  10°  from  east  and  west  magnetic.  Even  including  these  the  average 
direction  of  all  the  walls  is  within  a  third  of  a  degree  of  east  and  west,  or  north  and  south, 
according  to  the  present  direction  of  the  compass,  which  here  points  about  12°  east  of 
north.  The  explanation  of  this  orientation  possibly  lies  in  some  astronomical  phenom¬ 
enon.  The  ancient  Aztecs  observed  one  of  the  chief  feasts  of  the  year  early  in  May  at 
about  the  time  when  the  summer  rains  begin  in  the  City  of  Mexico.  Possibly  the  Hohokam 
observed  a  similar  festival.  At  any  rate,  early  in  May  and  again  about  the  first  of  August 
the  sun  sets  approximately  in  the  direction  of  the  main  walls  of  the  temples  and  houses  of 
the  Hohokam. 

The  study  of  the  ruins  of  the  main  Santa  Cruz  Valley  and  some  of  its  tributaries  led 
to  the  conclusion  that  a  mere  examination  of  the  map  was  sufficient  to  indicate  where 


GO 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


mins  would  be  found.  Accordingly  I  decided  upon  the  head  of  the  Rincon  Valley,  about 
22  miles  southeast  of  Tucson,  as  a  test  case.  The  expected  ruins  were  found  in  the  shape 
of  vestiges  of  several  small  villages,  the  chief  of  which  contains  the  foundations  of  at  least 
18  houses.  There  can  not  have  been  less  than  25  houses  in  this  small  mountain  valley,  and 
quite  possibly  more,  for  pottery  is  scattered  thickly  far  beyond  the  limits  of  the  founda¬ 
tions.  The  present  population  consists  of  two  American  and  two  Mexican  families.  One 
of  the  Americans  is  the  forest  ranger;  the  Mexicans  are  vaqueros,  or  cattle-men.  The  other 
American  is  the  only  man  who  does  much  farming.  He  says  that  the  cultivated  land 
amounts  to  200  acres,  but  his  individual  figures  tota’  only  150,  and  even  this  seems  in 
excess  of  the  visible  fields.  Granting  that  the  figures  are  correct,  however,  the  arable 
land  with  the  water  supplied  by  the  brook  might  suffice  for  a  population  such  as  that 
indicated  by  the  ruins.  Therefore  nothing  can  be  argued  either  for  or  against  changes 
of  climate.  Certain  other  phenomena,  however,  bear  directly  upon  the  subject.  About 
1.5  miles  east  of  the  forest  ranger’s  house  and  about  3  miles  east  by  north  of  the  prominent 
hill  called  Sentinel  Butte,  a  grassy  slope  drops  toward  the  northwest  at  the  base  of  Rincon 
Peak,  8,465  feet  high.  The  slope  has  a  fall  of  about  10°,  and  an  altitude  of  from  3,300  to 
3,500  feet  above  sea-level.  On  the  smoothest  part  of  it,  for  a  distance  of  about  half  a  mile 
parallel  to  the  upper  Rincon  and  for  a  width  of  about  one-half  or  two-thirds  as  much,  one 
finds  unmistakable  terraces  built  apparently  for  purposes  of  agriculture.  In  general  they 
are  from  20  to  70  feet  long  and  2  or  3  feet  high.  The  commonest  location  is  at  right  angles 
to  the  minor  drainage  lines,  each  little  swale  being  broken  into  terraces  with  a  width 
of  from  20  to  30  feet,  as  appears  in  Plate  2,  a.  In  some  cases  the  spaces  between  the 
swales  are  also  terraced.  The  terrace  walls  are  all  composed  of  pebbles  and  cobbles. 
I  searched  carefully  for  pottery,  but  succeeded  in  finding  only  one  or  two  coarse  bits, 
quite  in  contrast  to  the  abundant  potsherds  which  occur  not  only  among  the  foundations 
lower  down  in  the  valley,  but  all  along  the  borders  of  the  alluvial  plain.  The  only  other 
works  of  man  among  the  terraces  are  some  small  stone  circles  resembling  modern  mescal 
beds,  where  the  agave  is  cooked,  and  a  round  structure  7  feet  in  diameter.  The  whole 
hillside  closely  resembles  hundreds  in  Palestine,  Syria,  and  Asia  Minor,  or  in  Mexico  and 
South  America.  Even  the  httle  round  structure  with  its  small  doorway  resembles  the 
watchmen’s  shelters  in  the  terraced  fields  of  Syria.  There  can  scarcely  be  any  doubt  that 
the  terraces  were  designed  for  agriculture.  Apparent^  they  were  not  intended  for  irri¬ 
gation,  for  they  are  not  properly  arranged,  nor  does  there  appear  to  be  any  available  source 
of  water.  They  must  have  been  intended  for  dry  farming.  Near  the  main  village,  down 
in  the  valley  3  or  4  miles  away,  the  gravel  slope  just  east  of  the  gully  which  bounds  the 
village  on  that  side  is  interrupted  by  a  few  similar  terraces.  Apparently  dry  farming  was 
attempted  in  more  than  one  place. 

As  has  already  been  said.  Professor  Forbes,  of  the  Arizona  Experiment  Station,  states 
that  dry  farming  is  not  now  practicable  in  Arizona  except  by  means  of  most  careful  and 
expensive  methods  of  plowing  and  harrowing.  The  terraced  slope  in  the  upper  Rincon 
Valley,  because  of  its  proximity  to  the  mountains,  undoubtedly  receives  more  rain  than  do 
many  parts  of  the  country.  Over  on  the  east  side  of  the  Santa  Rita  Mountains,  at  an 
elevation  considerably  greater  than  that  of  our  terraces,  potatoes  are  said  to  be  cultivated 
without  irrigation,  but  further  inquiry  shows  that  they  are  watered  naturally  by  springs 
bursting  out  above  them.  In  the  same  region,  at  the  mouth  of  Gardner’s  Canyon,  at  an 
elevation  of  about  5,000  feet,  four  or  five  settlers  took  up  land  and  attempted  real  dry 
farming  in  1909.  The  elevation  is  sufficient  to  insure  moderately  cool  weather  much  of 
the  year  and  hence  less  evaporation  than  in  the  parching  plains.  The  rainfall  in  the 
summer  of  1909,  as  measured  at  the  Empire  Ranch  not  far  away,  amounted  to  9.39  inches 
as  against  an  average  of  7.93  for  the  preceding  15  years.  Nevertheless  the  corn  failed 
entirely;  and  the  beans,  the  most  reliable  of  all  crops,  gave  so  scanty  a  return  that  the 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


61 


farmers  were  completely  discouraged.  In  the  absence  of  records  of  rainfall,  we  can  not 
say  categorically  that  crops  might  not  be  raised  on  the  terraces  at  Rincon.  We  can  merely 
say  that  nothing  of  the  kind  has  succeeded  in  this  part  of  Arizona  hitherto,  and  that  in 
April  1910  we  found  the  terraces  with  no  more  sign  of  fresh  vegetation  than  was  apparent 
on  the  surrounding  dry  plains. 

The  hypothesis  may  be  advanced  that  the  Hohokam  here  cultivated  some  special  crop, 
such  as  wild  tobacco  or  some  native  plant  now  unknown,  a  plant  for  which  dry  conditions 
are  especially  favorable.  No  such  plant  is  now  known,  according  to  Dr.  MacDougal  and 
the  other  botanists  of  Tucson.  The  space  covered  by  the  terraces  is  so  large  that  we  can 
scarcely  assume  that  such  a  crop  would  be  of  sufficient  importance  to  require  so  great  an 
expenditure  of  effort.  Moreover,  so  far  as  is  known,  no  plant  after  having  once,  so  to 
speak,  been  made  a  part  of  man’s  equipment,  has  ever  escaped  from  cultivation;  accordingly 
we  must  pass  by  this  assumption  as  one  for  which  there  is  no  ground.  The  cultivation  of 
products  such  as  grapes  or  fruits  would  demand  irrigation  or  greater  rainfall. 

Apart  from  the  immediate  question  of  the  possible  climatic  significance  of  the  terraces, 
they  are  important  in  another  aspect.  Mankind  rarely  labors  except  under  strong  com¬ 
pulsion,  whether  of  hunger,  desire,  fear,  ambition,  or  love.  The  ancient  Hohokam  would 
scarcely  have  gone  to  the  labor  of  making  the  terraces  without  some  good  motive.  The 
obvious  agricultural  character  of  the  structures  precludes  the  idea  of  any  religious  signifi¬ 
cance,  as  does  the  fact  that  elsewhere  such  terraces  are  found  closely  associated  with  religious 
structures  from  which  they  are  clearly  different.  The  only  adequate  cause  for  the  terraces 
would  seem  to  be  the  need  of  more  abundant  areas  of  cultivation  or  the  desire  for  luxuries 
such  as  grapes.  Defense  apparently  had  nothing  to  do  with  the  matter,  for  there  seems  to 
be  no  fortress  near  at  hand,  and  the  terraces  are  not  in  a  particularly  defensible  position,  in 
fact  quite  the  contrary,  being  at  the  foot  of  a  mountain  side.  Accordingly,  it  seems  most 
probable  that  the  Hohokam  of  the  Rincon  Valley  found  that  the  land  at  their  disposal  was 
not  sufficient  for  their  needs.  Therefore,  having  somehow  learned  the  art  of  making 
terraces  as  practised  in  other  parts  of  the  arid  southwest  or  in  Mexico,  they  built  a  con¬ 
siderable  number,  partly  close  to  their  main  village,  but  chiefly  on  a  slope  of  especially 
favorable  location.  This  in  itself  may  seem  of  small  importance,  but  it  is  significant  as 
indicating  that  probably  the  population  was  decidedly  dense.  Had  there  been  an  abun¬ 
dance  of  unused  irrigable  land  either  in  the  Rincon  valley  or  in  the  neighboring  regions, 
the  Hohokam  would  scarcely  have  gone  to  the  labor  of  building  terraces. 

RUINS  IN  THE  DESERT  REGION  WEST  OF  TUCSON. 

Further  description  of  the  ruins  of  the  Santa  Cruz  Valley  would  add  no  new  types, 
although  it  would  show  more  conclusively  the  surprising  number  of  the  ancient  villages. 
Accordingly  we  shall  now  turn  to  other  regions  in  order  to  indicate  how  widespread  are 
evidences  of  an  apparently  numerous  population  in  the  distant  past.  About  60  miles 
southwest  by  west  of  Tucson,  the  little  Indian  oasis  of  Artesa  stands  in  the  midst  of  an  area 
of  thousands  of  square  miles  inhabited  only  by  Indians.  Nowhere  in  the  whole  region  is 
there  a  perennial  brook,  and  even  springs  are  of  the  utmost  rarity.  The  white  man  does 
not  live  here,  because  there  is  nothing  for  him  to  desire.  Here  and  there  he  has  made 
attempts  at  mining,  but  with  such  poor  success  that  in  practically  every  case  work  has  been 
abandoned.  Even  the  Indians  find  life  no  easy  matter.  One  or  two  thousand  of  them 
cluster  here  and  there  in  little  villages,  depending  for  part  of  the  year  upon  the  water  of 
broad,  shallow  reservoirs  filled  by  the  floods,  but  compelled  in  the  dry  seasons  to  resort  to 
the  mountain  valleys  and  drink  from  wells  dug  by  the  white  man’s  art.  As  they  sit  by 
their  smoky  fires  of  desert  bushes  they  talk  of  the  years  of  drought.  In  1903  and  1904, 
if  my  Indian  informant  had  the  dates  correctly,  no  rain  of  any  value  fell  from  the  end 


62 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  the  winter  showers  in  March  of  the  first  year  to  the  beginning  of  the  rains  of  the  second 
winter,  18  months  later,  in  October  or  November  of  the  succeeding  year.  The  Indians 
obtained  no  crops  whatever;  they  killed  or  sold  some  of  their  cattle,  got  credit  at  the  stores, 
or  went  off  to  work  in  the  mines.  They  would  have  starved  without  the  resources  furnished 
by  the  white  man;  they  would  have  perished  of  thirst,  had  they  been  forced  to  stay  in  the 
region  without  his  deeply  sunken  wells,  the  work  of  tools  of  iron.  We  can  scarcely  empha¬ 
size  too  strongly  the  dire  straits  to  which  the  Indians  would  to-day  be  driven  if  dependent 
only  upon  their  own  primitive  resources.  Even  in  the  well-watered  Santa  Cruz  Valley 
the  struggle  for  subsistence  would  be  hard  enough,  but  in  the  drier  regions  farther  west 
it  would  be  far  worse. 

In  spite  of  the  inhospitable  character  of  the  country  west  of  Tucson,  it  once  was  much 
more  densely  populated  than  now ;  at  least,  it  is  full  of  ruins.  I  shall  not  attempt  to  describe 
the  small  ones  in  the  immediate  vicinity  of  Artesa,  nor  shall  I  dwell  on  those  described  by 
various  persons,  including  Americans,  Mexicans,  and  Indians,  but  which  I  have  not  seen. 
A  few  lying  off  to  the  northwest  of  Artesa  will  serve  to  illustrate  all.  Beginning  at  a  point 
about  4  miles  northwest  of  Artesa,  a  fine  of  volcanic  buttes  extends  northward  with  plains 
on  either  side.  Floods  flow  past  them  from  the  low  mountains  of  Comovavi*  to  the 
northeast,  but  there  is  no  long-continuing  source  of  water  until  Nohk  is  reached,  11  miles 
from  Artesa.  Even  there  the  water  is  not  derived  from  springs  or  brooks,  but  from  a 
deep  well.  Nevertheless,  the  buttes  are  covered  with  defensive  walls  and  with  Uttle  in¬ 
closures  like  those  on  the  hills  above  the  villages  of  the  Santa  Cruz.  On  the  first  butte  we 
saw  from  50  to  100  of  the  little,  rudely  walled  platforms,  wherein  we  have  inferred  that 
families  took  refuge  in  time  of  danger.  Down  below  on  the  south  side  of  the  butte  we 
found  pottery  scattered  about,  not  thickly,  but  in  such  quantities  that  it  could  only  have 
been  left  there  by  long  occupation  of  the  site.  How  many  other  villages  and  forts  there 
may  be  is  unknown.  We  saw  defensive  walls  on  two  buttes,  and  a  prosperous  Indian  at 
Nolik  informed  us  that  they  are  found  on  many  others. 

Thirty  miles  to  the  northwest  of  Artesa  the  modern  village  of  Covered  Wells,  the 
home  of  the  Papago  chief,  spreads  its  scattered  houses  here  and  there  along  the  sides  of  a 
valley  in  the  Quijotoa  Mountains,  about  65  miles  west  of  Tucson.  As  usual  the  site  of  the 
modern  village  does  not  at  all  resemble  that  of  the  villages  of  the  past.  It  is  determined 
by  the  location  of  one  or  two  wells.  Close  to  the  modern  houses  no  sign  of  ruins  is  apparent, 
for  the  Hohokam,  unlike  the  modern  Indians,  deemed  good  land  as  necessary  as  good 
water.  Six  miles  east  of  the  upper  part  of  Covered  Wells,  however,  and  4  miles  from  the 
lower  village,  on  the  way  toward  Tucson,  an  Indian  youth  showed  us  the  ruins  of  Maisk, 
or  “  Hidden,”  as  the  name  was  interpreted  by  the  guide.  They  lie  far  out  from  the  moun¬ 
tains,  beyond  the  limit  of  stones  and  gravel,  where  the  soil  is  fine  and  fertile,  and  where  the 
floods  from  the  mountains  can  spread  abroad  and  water  the  plain.  Just  at  this  point  the 
road  runs  nearly  parallel  to  a  dry  “wash”  which  sometimes  brings  down  a  considerable 
quantity  of  flood  water.  At  present  no  attempt  at  cultivation  is  made  here,  although 
farther  down  the  wash,  where  the  floods  finally  spread  into  a  thin,  playa-like  sheet  and 
soak  slowly  into  the  ground,  the  Indians  from  the  villages  beside  the  wells  at  the  base  of 
the  mountains  five  for  a  time,  and  sow  their  seed.  Nevertheless,  for  three-quarters  of  a 
mile  at  Maisk  the  wash,  which  hes  just  south  of  the  road,  is  flanked  by  an  area  thickly 
strewn  with  pottery,  which  spreads  to  a  distance  of  nearly  1,000  feet  on  either  side.  In 
one  place  my  companion,  Mr.  Godfrey  Sykes,  of  the  Desert  Botanical  Laboratory,  found 
a  straight  channel  which  looked  as  if  it  might  have  been  an  irrigation  ditch.  In  another 
he  found  what  seemed  to  be  the  dam  of  a  simple  little  reservoir  3  or  4  feet  deep.  Such  a 
shallow  reservoir  can  not  have  remained  full  for  many  months,  for  one  15  feet  deep  at  the 
mountain  village  of  Comovavi  lasts  only  six  or  seven  months,  so  rapid  is  the  process  of 


*  Often  written  Comobabi,  properly  Com  Vahia. 


THE  RUINS  OF  SOUTHERN  ARIZONA. 


63 


evaporation.  If  the  houses  at  Maisk  were  on  an  average  100  yards  apart,  the  number 
must  have  been  80  or  90.  If  they  were  grouped  like  those  at  modern  Cababi  (properly 
Covavi)  or  at  the  ancient  village  of  Sabino,  the  number  would  have  been  nearly  450; 
or  if  like  those  at  the  ruins  near  Gibbon’s  Ranch,  600  or  more. 

The  ruins  of  A’ai  Sto,  or  '‘White  on  Both  Sides,”  as  our  guide  translated  it,  lie  some  3 
miles  southwest  of  Maisk  and  are  of  the  same  type  in  all  respects.  They  He  along  the 
sides  of  the  wash  which  comes  down  from  Quijotoa  post-office,  and  are  situated  just  below 
the  point  where  the  wash  crosses  the  road  from  the  Covered  Wells  to  the  old  pump-house 
of  the  abandoned  Logan  Mine.  I  walked  in  the  pottery-strewn  area  for  2,000  feet  and 
had  not  come  to  the  end  of  it.  SHght  mounds  at  the  upper  end,  here  as  at  Maisk,  suggest 
the  remnants  of  the  more  important  houses,  made  perhaps  of  adobe  plastered  upon  a 
wooden  frame,  or  even  made  into  walls  by  itself.  The  Indians  know  nothing  of  the  ruins 
save  that  they  have  always  been  just  as  they  are  to-day.  They  can  not  explain  why 
they  were  located  here  where  now  there  is  neither  water  to  drink  nor  land  sufficiently  watered 
for  cultivation.  When  I  asked  where  the  ancient  villages  got  their  water,  our  guide  from 
Jiuwak,  as  the  lower  part  of  Covered  Wells  is  called,  repHed  that  he  did  not  know.  The 
elders  of  his  village,  so  he  said,  were  of  the  opinion  that  the  Hohokam  brought  water  from 
a  spring  up  in  the  mountains  a  little  south  of  Quijotoa  post-office.  The  spring  Ues  3  or  4 
miles  from  Maisk  and  2  or  3  from  A’ai  Sto,  and  1,000  or  more  feet  above  either.  That 
this  should  have  been  the  main  source  of  water  for  two  large  villages  is  incredible.  To 
be  sure,  the  women  of  Comovavi  carry  water  a  mile  or  more  from  a  well  located  some 
400  or  500  feet  higher  than  the  village;  but  this  is  less  than  half  the  distance  required  at 
the  ancient  villages.  Moreover,  the  modern  village  is  located  as  near  to  the  well  as  is 
convenient,  which  is  not  the  case  with  the  ruins  in  respect  to  the  spring,  and,  finally,  Como¬ 
vavi  gets  its  water  for  seven  or  eight  months  from  reservoirs.  The  depth  of  these,  as 
already  mentioned,  enables  them  to  hold  water  much  longer  than  could  possibly  be  the 
case  with  such  shallow  reservoirs  as  could  be  constructed  at  the  ruins. 


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^-VV' 


CHAPTER  VIII. 


RUINS  IN  NORTHERN  SONORA  AND  SOUTHERN  NEW  MEXICO. 

Before  attempting  further  to  explain  the  facts  presented  in  the  preceding  chapter, 
let  us  consider  the  ruins  of  northern  Mexico.  The  little  town  of  Altar  (altar'),  132  miles 
southwest  of  Tucson  as  measured  by  automobile,  is  the  metropolis  of  the  dry  north¬ 
western  corner  of  Mexico.  So  long  has  this  site  been  inhabited  that  the  soil  contains  a 
surprising  abundance  of  pottery.  The  flat  adobe  roofs  of  some  of  the  houses  are  so  full 
of  it  that  one  walks  on  it  as  on  a  pavement.  Twenty-two  miles  farther  to  the  southwest 
the  last  inhabited  place  of  any  size  on  the  Altar  River  is  reached  at  Caborca.  Here,  too, 
indications  of  ancient  occupation  abound,  and  the  hills  on  both  sides  of  the  town  show  a 
few  little  walled  inclosures  for  defense.  From  this  point  to  the  Gulf  of  California  there  is 
no  village  properly  speaking,  although  the  distance  is  over  50  miles.  Our  visit  to  the 
Altar  Valley  was  made  at  the  suggestion  of  Dr.  MacDougal,  who  had  heard  and  read 
enough  of  it  to  feel  sure  that  it  would  be  a  good  region  in  which  to  test  the  conclusions 
reached  along  the  Santa  Cruz.  After  the  upper  parts  of  the  valley  had  been  seen  under 
the  competent  guidance  of  Mr.  H.  Harrison,  of  Caborca,  a  trip  was  made  down  the  river 
to  the  sea  in  order  to  test  our  conclusions.  At  Cerro  Tortuga,  near  the  so-called  “Port" 
of  Lobos  on  the  uninhabited  shore  of  the  Gulf,  we  had  seen  a  remarkable  group  of  ancient 
graves  of  wholly  unknown  origin.  In  the  immediate  valley  of  the  lower  Altar,  however, 
we  could  hear  of  no  ruins  aside  from  those  of  a  Spanish  Mission  at  Buzani,  about  14  miles 
southwest  of  Caborca.  Except  for  two  or  three  Mexican  cattle  ranches,  the  great  plain 
extending  thence  for  40  miles  to  the  sea  is  an  uninhabited  desert.  It  seemed  likely,  never¬ 
theless,  that  if  the  chmate  was  formerly  more  propitious  than  now,  the  region  once  con¬ 
tained  villages.  Accordingly  we  drove  down  the  dry  river  to  the  Gulf  of  Cahfornia. 

At  Buzani,  in  the  midst  of  the  monotonous  expanse  of  the  modern  alluvial  flood-plain, 
we  found  one  Mexican  and  five  or  six  Papago  famihes  living  with  their  cattle  beside  a  well 
about  200  feet  deep.  They  were  raising  the  water  in  great  leather  buckets,  drawn  by 
horses.  The  poor  beasts  had  no  collars,  but  were  forced  to  pull  with  the  whole  dead  weight 
of  the  bucket  attached  to  the  pommels  of  their  tightly  girthed  saddles.  In  good  years 
several  hundred  acres  can  be  cultivated  here,  but  in  1910  we  found  that  nothing  had  been 
planted,  because  of  the  lack  of  winter  rain.  Half  a  mile  to  the  north,  on  the  low  gravelly 
terrace  bounding  the  silty  plain,  the  old  mission  church  stands  in  the  midst  of  the  ruins 
of  a  village.  Inside  the  church  little  wooden  images  mark  the  graves  of  newly  departed 
Papagos,  while  an  offering  of  a  few  cigarettes  shows  that  the  modern  Indian  is  still  a  pagan. 
Outside  the  ruined  mud  edifice  pottery,  sea-shells,  and  metate  stones  of  lava  cover  a  space 
of  30  to  40  acres.  Immediately  around  the  church  numerous  heaps  still  mark  the  sites  of 
fallen  houses;  some  are  almost  obliterated  and  only  the  church,  being  well  built  of  adobe 
bricks,  stands  firmly.  Doubtless  the  houses  date  back  little  more  than  a  century.  The 
pottery  is  not  the  old  sort  with  brown  ornaments  painted  upon  it,  but  consists  of 
coarse,  unadorned  modern  varieties,  intermingled  with  a  few  bits  of  cheap  ware  with  a 
green  or  yellow  glaze.  We  counted  18  mounds  close  to  the  mission,  and  estimated  the 
number  of  dwellings  in  the  adjacent  area  of  recent  occupation  to  be  from  40  to  60.  Except 
in  one  respect,  these  ruins  have  no  special  significance.  Doubtless  in  part  they  date  back 
to  very  early  times,  but  the  last  occupation,  in  the  time  of  the  Mission,  can  scarcely  go  back 
more  than  150  years.  This  leads  us  to  query,  “Why  was  the  Mission  ever  estabhshed  here 

6  65 


66 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


where  there  is  so  little  water?  Missions  are  usually  located  in  the  best  places  in  the 
country,  where  villages  still  prosper.  Here,  on  the  contrary,  a  permanent  village  was 
impossible  before  the  days  of  wells.  At  most  the  Indians  could  only  live  here  for  a  few 
months  during  the  flood  season;  their  permanent  village  must  have  been  elsewhere.  Why, 
then,  should  so  substantial  a  mission  have  been  established?  Also  why  is  there  no  well 
close  to  it,  but  only  a  canal  which  is  dry  most  of  the  year?  The  only  answer  seems  to 
be  that  probably  in  the  latter  half  of  the  eighteenth  century,  when  the  Spanish  fathers 
came  this  way,  a  longer  or  shorter  period  of  abundant  precipitation  had  produced  a  supply 
of  water  somewhat  greater  than  exists  at  present.  We  are  far  from  saying  that  this  indi¬ 
cates  a  change  of  climate  in  so  short  a  time  as  a  century  and  a  half;  yet  it  seems  to  sug¬ 
gest  that  fluctuations  of  fairly  long  period  are  now  in  progress,  and  that  in  the  eighteenth 
century  the  country  was  blessed  with  a  period  when  the  rainfall  for  a  while  was  somewhat 
more  abundant  than  during  the  average  seasons  of  the  last  three  or  four  score  years. 

Below  Buzani  no  agriculture  is  carried  on  to-day:  the  floods  are  too  uncertain  to 
make  it  worth  while  for  any  one  to  attempt  to  rely  on  farming,  although  one  or  two  cattle- 
ranchers  plant  a  little  grain  if  water  happens  to  be  abundant.  Nevertheless,  about  10 
miles  below  Buzani,  above  the  ranch  of  Alamo  San  Francisco,  we  discovered  a  ruin  of  the 
regulation  type.  The  natives  apparently  knew  nothing  of  it,  but  by  searching  along  the 
terrace  corresponding  to  the  one  where  most  of  the  ruins  are  situated,  we  found  it.  For 
over  a  mile  it  stretches  east  and  west  beside  the  dry  stream-bed,  while  the  width,  as  usual,  is 
only  about  a  third  of  the  length.  Practically  the  whole  of  this  large  area  is  thickly  covered 
with  artifacts,  chiefly  pottery  of  the  same  type  as  in  the  Santa  Cruz  ruins,  but  with  a  few 
new  patterns.  Shells  of  clams  and  other  animals  also  abound,  indicating  proximity  to  the 
sea.  Another  notable  feature  is  numerous  patches  of  hard  clay  about  3  feet  in  diameter. 
They  are  burned  to  a  red  color  to  a  depth  of  from  4  to  6  inches  and  appear  to  be  fire-places. 
Judging  by  modern  fire-places,  such  a  depth  of  burning  must  indicate  prolonged  or  constant 
use.  Besides  these  there  are  numerous  other  round  beds  of  small  cobbles,  which  may  also 
be  fire-places.  Often  these  are  in  ruins  and  charcoal  is  mingled  with  the  stones.  The 
number  of  inhabitants  may  have  been  considerable.  The  area  of  the  village  is  greater  than 
that  of  modern  Caborca,  whose  population,  according  to  Mr. Harrison,  may  be  conservatively 
estimated  at  about  1,500.  The  number  of  fire-places  and  the  thickness  of  the  pottery  suf¬ 
ficiently  indicate  a  dense  population.  If  the  houses  were  as  near  together  as  at  the  little 
village  of  Sabino  near  Tucson,  which,  it  will  be  remembered,  was  less  densely  peopled  than 
most  of  the  ruins,  the  number  of  families  was  probably  at  least  400. 

Another  old  town,  San  Francisco,  is  found  4  or  5  miles  below  Alamo  San  Francisco, 
and  still  farther  from  any  visible  source  of  water.  Its  essential  features  are  like  those  of 
the  neighboring  ruin,  save  that  no  clay  fire-places  were  noted,  only  those  of  cobble-stones. 
This  ruin  is  smaller  than  the  other,  only  about  2,000  feet  long,  and  the  pottery  is  not  so 
thickly  strewn. 

Below  San  Francisco  we  found  no  pottery  or  evidences  of  ancient  occupation  for  about 
25  miles.  Possibly  ruins  exist  and  were  missed  because  we  followed  the  sandy  wagon 
trail  and  could  not  inspect  the  edge  of  the  terrace  for  miles  at  a  time.  Finally,  at  Disem- 
boque,  near  the  mouth  of  the  river,  pottery  appears  once  more.  How  great  an  area  it 
covers  is  not  certain,  but  it  is  widely  spread.  A  little  more  than  a  mile  from  the  sea  the 
dry  channel  of  the  Altar  breaks  through  a  ridge  of  sand-dunes  15  to  20  feet  high,  which 
apparently  mark  the  line  of  an  old  strand  located  5  or  10  feet  above  the  present  level  of 
the  Gulf  of  California.  At  places  the  old  strand  and  that  of  to-day  come  close  together, 
but  usually  they  are  distinct.  Possibly  there  has  not  been  an  actual  change  in  the  level 
of  the  sea,  but  merely  a  building  out  of  a  delta  by  the  river.  At  any  rate,  when  the  Hoho- 
kam  dwelt  here,  the  seashore  seems  to  have  been  farther  inland  than  now.  Habitations 
were  built  close  to  it,  as  is  proved  by  the  great  abundance  of  pottery.  Here,  if  one  may 


EUINS  IN  NOETHERN  SONORA  AND  SOUTHERN  NEW  MEXICO. 


67 


judge  from  the  heaps  of  shells,  the  people  gathered  to  feast  on  clams,  oysters,  and  half  a 
dozen  other  kinds  of  shell-fish.  At  first  one  surmises  that  there  may  have  been  no  real 
village,  for  the  Hohokam  may  merely  have  come  to  the  shore  to  gather  shell-fish,  but  this 
is  not  the  case.  Undoubtedly  the  shell-fish  were  an  important  item  in  the  food  supply  of  the 
ancient  people.  Often  they  gathered  one  special  variety,  such  as  razor  clams,  and  perhaps 
ate  it  exclusively,  leaving  other  kinds  for  other  feasts,  as  appears  from  the  character  of 
the  shell-heaps.  Back  from  the  shore,  however,  signs  of  an  agricultural  village  are  visible 
in  the  form  of  pottery  scattered  thickly  for  a  distance  of  a  mile  or  more.  Shells,  on  the 
other  hand,  are  no  more  abundant  than  in  the  villages  many  miles  in  the  interior,  which 
would  scarcely  be  the  case  if  the  Hohokam  had  come  here  merely  to  get  food  from  the  sea. 
The  pottery  is  found  chiefly  on  slightly  elevated  tracts  5  to  15  feet  above  the  general  level. 
Apparently  some  sort  of  erosion,  presumably  eolian,  has  carried  away  much  of  the  soil, 
leaving  hollows,  which  have  since  been  partially  filled  by  deposition  from  the  floods  of  the 
river.  Possibly  this  condition  existed  when  the  Hohokam  lived  here;  they  may  have 
built  their  houses  on  the  high  places  and  cultivated  the  low  ones.  One  thing  at  least  is 
clear:  many  people  lived  here  whose  interest  was  apparently  not  in  being  close  to  the  sea, 
but  in  being  close  to  land  which  then  was  presumably  arable  and  now  would  be  highly  pro¬ 
ductive  if  only  it  were  supplied  with  water. 

Taken  as  a  whole  the  conditions  of  the  lower  Altar  are  like  those  of  the  lower  Santa 
Cruz.  According  to  tradition,  the  whole  plain  of  the  lower  Altar  was  once  under  culti¬ 
vation  by  the  Papagos  or  their  predecessors.  The  tradition,  however,  as  related  by  the 
Mexicans,  is  not  at  all  definite,  and  may  have  no  foundation  other  than  observation  of  the 
phenomena  which  have  been  described  above.  No  one  who  carefully  examines  the  region 
can  fail  to  be  impressed  by  the  abundance  of  ruins,  the  care  with  which  they  are  so  located 
as  to  command  the  best  agricultural  land,  and  the  hopelessness  of  now  attempting,  by 
means  of  primitive  methods  of  cultivation,  to  support  even  a  handful  of  families  in  the 
regions  where  the  Hohokam  once  seem  to  have  been  numerous. 

Phenomena  which  may  have  a  bearing  on  the  question  of  changes  of  climate  are  found 
not  only  below,  but  above  the  present  lower  limit  of  cultivation  in  the  valleys  of  the  Altar 
and  its  tributaries.  Chief  among  these  are  the  so-called  trincheras  or  terraced  hills. 
One  such  is  said  to  be  located  near  Altar,  but  that  which  will  here  be  described  lies  farther 
to  the  south  in  the  Magdalena  Valley.  From  Altar  it  is  reached  by  a  ride  of  14  miles  south¬ 
ward  to  the  Magdalena  River,  and  then  southeast  up  the  river  for  21  miles.  Much  of  the 
way  the  road  leads  through  a  beautiful  country,  which  would  deceive  the  uninitiated  into 
the  belief  that  it  is  the  best  of  farm  land.  The  fine,  fertile  soil  is  well  covered  with  short, 
thick  grass,  which  in  early  May  1910  had  been  dry  and  brown  since  the  end  of  the  rains 
of  the  previous  summer.  Even  in  better  seasons  than  1909-10  the  rain  does  not  last  long 
enough  to  enable  crops  to  be  raised  without  irrigation,  except  in  the  very  best  years. 

The  Trinchera  is  a  dark  rugged  hill  rising  600  feet  above  the  smooth  plain,  while  smaller 
hills  flank  it  to  the  east  and  southwest.  The  slopes  of  all  the  hills  are  divided  into  in¬ 
numerable  terraces,  the  work  of  an  ancient  people.  To  the  north  the  broad  alluvial  plain 
of  the  Magdalena  is  covered  with  fields  of  waving  wheat,  or  with  brown  patches,  left 
unsown  for  lack  of  water  for  irrigation.  Not  far  from  the  base  of  the  hills  lie  the  mud 
houses  and  square  corrals  of  a  Mexican  village,  while  the  brush  shanties  of  an  Indian  hamlet 
are  located  a  little  farther  away.  (See  Plate  2,  c.) 

Long  ago  a  branch  of  the  Hohokam  lived  here.  In  some  respects  they  differed  from 
their  northern  brethren  in  Arizona,  but  not  essentially.  Among  the  sparsely  scattered 
bits  of  pottery  which  we  found,  we  noted  none  painted  with  the  ordinary  brown  designs. 
The  only  decorated  piece,  picked  up  by  Mr.  Harrison,  was  adorned  with  a  rectangular 
pattern  of  red,  blue,  and  black,  and  was  more  complex  than  anything  that  we  saw  elsewhere. 
The  Hohokam  of  the  Trincheras  used  metates  and  manos  for  grinding  corn  and  beans,  just 


68 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


as  did  their  neighbors  100  to  200  miles  to  the  north.  They  hkewise  constructed  temples 
oriented  with  the  long  walls  pointing  toward  the  place  where  the  sun  sets  in  May.  Yet 
they  differed  from  the  people  of  southern  Arizona  in  that  they  were  more  skilled  in  the 
arts  of  wall-building,  defense,  and  agriculture. 

The  Great  Trinchera  is  of  special  interest  because  it  appears  to  combine  three  t3rpes 
of  structures,  religious,  military,  and  agricultural.  Possibly  traces  of  houses  may  also  be 
visible,  but  we  detected  none.  The  hill  is  somewhat  crescent-shaped,  about  1,800  feet  long 
from  point  to  point  of  the  crest,  and  lying  with  the  concave  side  facing  almost  due  north 
toward  the  distant  river.  Beginning  at  the  base  of  the  steep  slope  on  the  north  side, 
about  20  terraces  rise  one  above  another.  Some  are  5  feet  high,  and  some  15;  some  10  feet 
wide,  and  others  20  or  30.  Below  these  main  terraces  the  ground  slopes  more  gently  than 
above.  Just  where  the  slope  changes,  and  in  the  center  of  the  concavity  of  the  hill,  the 
Hohokam  built  what  seems  to  have  been  a  temple  or,  better,  a  ceremonial  platform,  an 
almost  rectangular  structure  with  a  length  of  about  165  feet  and  a  width,  from  north  to 
south,  of  30  feet  at  one  end  and  40  at  the  other,  a  shape  appropriate  to  a  narrow  terrace. 
Rude  walls  of  boulders  piled  up  without  cement  surround  the  platform,  and  are  pierced 
by  a  door  at  the  western  end;  while  in  the  center  of  the  north  side  a  circular  inclosure, 
12  feet  in  diameter,  with  a  door  to  the  south,  appears  to  have  been  the  holy  place.  From 
all  points  of  view  the  ceremonial  platform  stands  out  prominently,  because  it  is  the  only 
place  from  which  all  the  stones  have  been  carefully  cleared.  Its  character  is  here  empha¬ 
sized,  because  it  seems  so  plainly  to  be  a  rehgious  or  ceremonial  structure,  and  as  such  is 
strongly  differentiated  from  all  other  structures  on  the  hill.  The  portion  of  its  walls 
composed  of  stone  was  probably  never  more  than  4  or  5  feet  high,  for,  with  the  poor  mate¬ 
rials  at  their  command,  the  Hohokam  apparently  could  not  build  much  higher  without 
mortar  to  bind  the  stones  or  tools  to  square  them.  The  gentle  slope  below  the  temple  is 
broken  into  terraces  like  those  on  the  steep  slopes  above,  except  that  they  are  only  1  or  2 
feet  high  and  20  to  50  feet  wide  in  accordance  with  the  angle  of  descent.  We  shall  discuss 
their  purpose  later. 

In  early  days  the  Hohokam  of  the  Trinchera  may  perhaps  have  been  as  unwarlike  as 
those  of  Charco  Yuma,  but  they  certainly  lived  to  learn  the  art  of  defense.  The  crest  or 
ridge  of  the  hill  is  strongly  fortified.  Nine  successive  walls  surround  the  main  hiUtop  at 
the  western  end.  On  the  central  part  of  the  ridge,  above  the  concavity  in  which  lies  the 
temple,  the  Hohokam  built  a  fort,  breast-high,  with  walls  6  feet  thick  and  with  a  circular 
'  bastion  projecting  from  it  on  the  exposed  south  side.  Here  and  there  on  the  terraces 
little,  low,  circular  inclosures,  like  those  among  the  Rincon  terraces,  may  have  been  of 
service  as  outposts.  Just  how  the  Hohokam  fought  we  do  not  know,  but  Mr.  Harrison 
found  a  collection  of  small  cobble-stones  1.5  to  2  inches  in  diameter,  just  the  right  size  to 
throw.  Evidently  they  were  brought  up  the  hill  for  some  special  purpose,  which  can 
scarcely  have  been  anything  but  defense. 

We  now  come  to  the  question  of  the  purpose  of  the  terraces.  Obviously  they  are  not 
for  religious  purposes,  for  the  one  religious  structure  is  clearly  differentiated  from  them. 
They  are  equally  differentiated  from  the  mihtary  portion  of  the  structures  on  the  hill. 
None  of  them  are  protected  by  walls,  and  the  lower  ones  (a  foot  or  two  high)  would  render 
practically  no  defensive  aid  whatever.  Are  they  for  habitation?  According  to  local 
tradition  the  Trinchera  is  a  species  of  Tower  of  Babel.  When  the  flood,  or  possibly  a  flood, 
overwhelmed  the  country,  the  Hohokam  took  refuge  on  the  hills  and  made  for  themselves 
dwelling-places.  There  is  no  reason,  however,  to  suppose  that  the  terraces  were  ever 
inhabited  except  temporarily.  In  the  first  place,  pottery  is  too  scarce  to  justify  such  a 
supposition;  in  the  second  place,  the  shape  is  not  adapted  to  habitation,  for  some  of  the 
terraces  are  so  narrow  that  there  is  scarcely  room  even  for  a  tiny  hut,  and  many  terraces 
taper  to  a  point  in  a  way  wholly  unsuited  to  houses.  Finally,  the  whole  aspect  of  the  ter- 


RUINS  IN  NORTHERN  SONORA  AND  SOUTHERN  NEW  MEXICO. 


69 


races  strongly  suggests  that  their  purpose,  like  that  of  the  ones  at  Rincon,  is  for  agriculture. 
The  terraces  of  the  Trinchera  closely  resemble  those  built  for  agricultural  purposes  on 
innumerable  hillsides  in  all  parts  of  Asia  and  in  some  of  the  other  continents,  and  the  re¬ 
semblance  is  so  close  that  strong  evidence  would  be  required  to  prove  that  the  purpose  in 
one  case  was  different  from  that  in  the  other.  Two  facts  tend  to  confirm  this  conclusion. 
In  the  first  place  the  terraces  are  almost  lacking  on  the  hot,  sunny  south  side.  This  does 
not  pertain  to  the  whole  south  side,  but  only  to  the  portions  which  have  a  steep  slope 
and  would  consequently  be  dry.  Secondly,  the  terraces  extend  as  far  as  the  slope  con¬ 
tinues,  and  then  merge  smoothly  into  unquestionable  agricultural  land.  On  the  west, 
north,  and  east  the  land  is  even  now  capable  of  cultivation,  and  could  be  irrigated  if  the 
Mexicans  chose  to  use  it  rather  than  to  employ  the  better  land  actually  in  use.  On  the 
south  the  hillside  ends  in  a  genuine  bahada,  whose  lower  portion  is  of  gentle  slope  and  of 
fairly  good  soil,  although  full  of  boulders  and  gravel.  When  walking  across  this  one  notices 
nothing  special  unless  his  attention  has  first  been  called  to  it,  but  when  viewed  from  above, 
the  land  is  seen  to  be  neatly  divided  into  rectangles,  presumably  fields,  about  40  feet  wide  and 
100  or  more  long  in  the  direction  of  the  slope.  So  distinct  are  these  that  they  can  be  clearly 
seen  in  photographs.  Inasmuch  as  the  rectangles  can  be  detected  only  from  an  eminence,  it 
is  possible  that  many  more  exist  elsewhere  undiscovered.  Russell*  describes  what  appear 
to  be  similar  old  fields  far  to  the  north,  beyond  the  Gila  River.  Taking  account  of  all  the 
facts,  it  seems  as  if  both  the  terraces  and  the  rectangles  were  designed  for  agriculture.  If 
this  were  so,  dry  farming  must  have  been  practicable  then,  although  now  it  is  out  of  the 
question.  Here,  as  at  Rincon,  the  Hohokam  may  have  desired  to  increase  the  area  of  cul¬ 
tivation  because  of  growth  of  population,  or  they  may  have  desired  to  cultivate  special 
products,  such  as  grapes.  Possibly,  also,  they  may  merely  have  wished  to  have  a  certain 
amount  of  land  immediately  under  the  shelter  of  their  fort,  so  that  at  least  a  small  crop 
might  be  safe  in  times  of  invasion.  This  last  supposition  is  somewhat  doubtful,  however, 
for  the  neighboring  httle  hills,  one  of  them  at  least  half  a  mile  away,  are  also  terraced, 
but  have  no  defensive  works. 

One  further  possibility  suggests  itself:  Did  the  Hohokam  women  carry  water  up  on 
the  hillsides  and  irrigate  the  terraces  in  times  of  drought?  The  estimates  of  our  party 
as  to  the  amount  of  land  available  for  cultivation  on  and  around  the  main  hill  in  the  terraces 
and  rectangles  varied  from  150  to  350  acres.  Including  also  the  other  hills  the  total  amount 
can  scarcely  be  less  than  200  acres,  none  of  which  could  possibly  be  watered  by  any  means 
except  the  actual  pumping  or  carrying  of  water.  Of  course  the  Hohokam  would  have  had 
to  carry  it,  and,  judging  by  other  primitive  races,  the  women  would  have  done  the  work. 
The  fields  lie  at  all  elevations  up  to  400  feet  above  the  plain,  and  at  various  distances  up 
to  nearly  a  mile  from  where  canals  could  be  located.  It  is  hardly  to  be  expected  that  a 
woman  should  make  a  round  trip  aggregating  on  an  average  about  half  or  three-quarters 
of  a  mile,  carry  her  olla,  or  water  jar,  all  that  distance,  climb  at  least  100  feet,  pour  out 
the  water  carefully  around  each  hill  of  beans  or  stalk  of  corn,  gossip  with  her  neighbors, 
and  get  back  to  the  canal  or  river  in  less  than  an  hour.  Suppose  also  that  each  woman 
worked  10  hours  a  day,  which  she  could  scarcely  do  in  conjunction  with  her  other  tasks  of 
grinding  flour  and  cooking  bread;  and  finally  suppose  that  in  three  weeks’  time  the  ground 
was  to  receive  the  equivalent  of  half  an  inch  of  rain,  or  in  other  words  that  each  square 
foot  received  1.25  quarts.  The  ordinary  load  for  a  woman  is  4  gallons.  Therefore  16 
women  would  have  to  work  10  hours  a  day  for  3  weeks  to  water  a  single  acre.  This  means 
that  in  order  to  keep  the  land  around  the  hill  watered  in  a  dry  season  over  3,000  women 
would  have  to  be  at  work  10  hours  a  day.  Counting  the  women  who  could  not  work  for 
various  reasons,  or  who  were  otherwise  engaged,  it  appears  that  the  number  of  women  old 
enough  to  work  would  have  had  to  be  toward  5,000,  which  means  a  total  population  of 


*  Frank  Russell:  The  Pima  Indians.  26th  Ann.  Rep.  Am.  Bureau  of  Ethnology,  Washington,  1908,  pp.  87  88. 


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THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


perhaps  15,000,  where  now  there  are  scarcely  more  than  200.  Rather  than  accept  the 
supposition  of  artificial  irrigation,  we  may  well  believe  it  probable  that  dry  farming  was 
actually  possible. 

The  case  of  the  Trinchera  is  not  like  that  of  Rincon  in  one  respect.  There  the  terraced 
area  receives  more  rain  than  the  surrounding  areas,  because  of  its  location  at  the  base  of 
high  mountains.  Here  the  Trinchera  lies  out  in  the  midst  of  a  plain,  far  from  the  moun¬ 
tains.  Moreover,  the  mountains,  when  reached,  are  not  of  great  elevation.  Hence  the 
terraces  and  the  old  rectangular  fields  receive  no  more  rain  than  the  rest  of  the  country. 
If  dry  farming  was  practicable  there,  it  was  practicable  elsewhere.  In  that  case  we  ought 
to  find  old  fields  in  other  places,  that  is,  in  the  neighborhood  of  all  the  chief  centers  of 
ancient  population.  According  to  report,  trincheras  are  abundant  all  over  northwestern 
Mexico,  although  they  do  not  appear  to  have  been  examined  closely.  Many  may  be  so 
ruined  that  they  have  escaped  notice.  On  the  upper  Magdelena,  at  a  place  known  as 
Terenate,  I  found  such  an  one  by  accident.  Climbing  a  high  hill  to  get  the  view,  I  was 
surprised  to  find  a  rude  defensive  wall  on  its  top,  and  fallen  terraces  on  the  sides.  The 
terraces  were  so  broken  as  to  be  almost  unrecognizable  had  it  not  been  for  their  resemblance 
to  those  of  the  Great  Trinchera.  Being  roughly  constructed  without  mortar,  and  being 
probably  of  great  age,  they  have  fallen  badly  to  ruins,  but  one  can  still  readily  find  places 
where  stone  has  been  piled  upon  stone  by  human  hands,  forming  terraces  of  precisely  the 
kind  described  above.  How  many  other  such  sites  exist  no  one  can  tell;  already  enough 
have  been  discovered  to  indicate  that,  granting  that  the  terraces  were  designed  for  agri¬ 
culture,  dry  farming  must  have  been  practised  on  a  small  scale  over  a  wide  area  where  it 
is  now  out  of  the  question. 

Thus  far  we  have  considered  the  ruins  in  the  desert  region  near  Tucson  in  southern 
Arizona,  and  to  the  southwest  and  south  of  that  town  across  the  border  in  northern 
Mexico.  Let  us  now  consider  the  region  lying  at  an  equal  or  greater  distance  to  the  east 
of  Tucson  in  southern  New  Mexico.  So  far  as  the  ruins  are  concerned  no  new  types  are 
found,  and  the  description  of  those  in  the  Santa  Cruz  Valley  applies  almost  unchanged 
to  those  in  southern  New  Mexico  Nevertheless  it  is  worth  while  to  present  some  of  the 
details  in  order  to  bring  out  more  fully  the  wide  extent  and  large  number  of  the  phe¬ 
nomena  upon  which  we  may  rely  in  our  study  of  the  past  as  compared  with  the  present. 
Before  taking  up  the  ruins,  however,  it  may  be  well  to  lay  at  rest  an  archeological  ghost 
which  finds  shelter  in  various  reputable  pubhcations. 

The  Animas  “dam,’'  or  “levee,”  lies  chiefly  in  the  extreme  southwestern  corner  of 
New  Mexico,  but  projects  a  short  distance  across  the  border  into  Mexico.  It  has  been 
described  as  a  huge  dam  made  to  hold  water  for  irrigation,  or  as  a  great  dike  upon  the  top 
of  which  water  was  carried  in  a  semicircular  course  across  the  head  of  the  Animas  Valley. 
In  the  midst  of  the  broad,  flat  plain  forming  the  bottom  of  the  valley  it  rises  in  the  form 
of  a  great  embankment  varying  in  height  from  15  to  50  feet.  From  the  foot  of  the  Lang 
Mountains  on  the  south  side  in  Mexico  it  sweeps  around  in  a  great  curve,  broken  for  a 
quarter  of  a  mile  on  the  southwest,  where  the  Cloverdale  drainage  breaks  through  it,  and 
then  continues  unbroken  until,  after  a  course  of  about  16  miles,  it  swings  around  to  the 
mountains  once  more,  and  then  merges  in  a  bluff  which  continues  to  the  other  end  of  the 
supposed  dam.  To  build  such  a  structure  would,  by  actual  computation,  require  the  work 
of  1,000  men  for  50  to  100  years.  The  physiographer,  however,  needs  no  such  computation 
to  prove  that  the  “dam”  is  not  of  human  origin.  It  presents  the  characteristic  features 
of  a  lacustrine  strand,  much  exaggerated,  however,  but  still  unmistakable.  At  some 
past  time,  presumably  during  the  glacial  period,  a  lake  must  have  stood  here,  and  must 
have  been  swept  by  winds  of  unusual  severity,  forming  beaches  of  exceptional  dimensions. 

The  actual  number  of  people  who  at  any  time  lived  in  the  entire  Animas  Valley  probably 
never  exceeded  1,000,  although  that  is  decidedly  more  than  live  there  to-day.  Ruins  of 


RUINS  IN  NORTHERN  SONORA  AND  SOUTHERN  NEW  MEXICO. 


71 


two  small  villages  are  located  near  the  dry  lake.  One  village,  a  mere  hamlet,  lay  on  the 
east  shore  at  the  top  of  the  highest  and  sandiest  part  of  the  beach.  Apparently  the  reason 
for  its  location  in  this  place  was  that  sandy  soil  holds  the  moisture  better  than  dry,  and 
hence  is  good  for  agriculture.  The  ruins  of  the  other  village  lie  on  Cloverdale  Creek,  about 
2  miles  west  of  the  old  shorehne.  In  general  they  are  like  those  already  described,  but 
the  pottery  is  different  and  the  houses  appear  to  have  contained  a  greater  proportion  of 
adobe  and  less  wood  or  branches  than  those  farther  west.  Moreover,  the  people  do  not 
seem  to  have  lived  in  individual  houses,  but  in  small  communal  dwellings,  as  was  the 
almost  universal  practise  farther  north.  The  village  covered  an  area  about  150  or  200  feet 
north  and  south  by  400  east  and  west.  The  abundant  but  highly  fragmentary  pottery  is 
mostly  of  a  red  variety  with  incised  lines  or  dots.  A  little  is  yellow  with  black  lines  of 
ornamentation,  or  else  red  with  black  or  brown  designs  upon  it.  Much  of  it  has  been 
carefully  polished.  The  number  of  separate  buildings  is  not  certain,  but  seems  to  have 
been  from  8  to  10.  Each  one  probably  contained  several  families,  and  the  largest  may 
have  housed  as  many  as  10.  To-day  the  possibilities  of  agriculture,  according  to  the 
one  settler  who  lives  near  at  hand,  are  most  meager.  During  the  three  winters  preceding 
our  visit  in  the  spring  of  1911  there  had  been  no  running  water.  The  summers,  however, 
had  been  better,  since  only  one  during  the  past  seven  had  been  absolutely  without  water. 
Generally  a  flowing  stream  comes  down  about  four  times  each  summer.  From  200  to  250 
acres  of  land  are  considered  capable  of  cultivation,  but  during  many  years  no  corn  whatever 
is  grown,  only  a  little  milo  maize  and  sugar-cane  for  fodder,  and  a  few  beans  for  human 
consumption.  The  universal  opinion  among  the  inhabitants  of  this  region  seems  to  be 
that  no  one  can  live  here  without  animals  of  some  sort  as  his  main  reliance.  The  owner 
of  a  pig  ranch,  with  whom  we  spent  a  night  in  the  center  of  the  old  lake-bed,  expressed 
himself  forcibly  to  the  effect  that  if  it  had  not  been  for  his  pigs  he  would  have  been  starved 
out  and  forced  to  leave  the  country.  “If  a  man  had  to  rely  on  what  he  could  raise  to  eat, 
lots  of  years  he  couldn’t  raise  it.  Last  year  I  got  no  rain,  and  didn’t  even  raise  a  mess 
of  beans.” 

Even  the  animals  suffer  severely.  The  year  1891  is  said  to  have  been  the  worst  in 
recent  times,  but  1892  was  also  bad,  as  was  1910,  while  in  1904  the  wells  in  all  parts  went 
dry  or  merely  gave  a  seep  of  water  insufficient  to  water  cattle.  Thousands  of  cattle  died. 
The  “Diamond  A”  ranch  lost  15,000  out  of  40,000  to  50,000  animals,  and  also  failed  to 
rear  any  of  the  calves,  which  usually  number  about  12,000.  The  animals  died  in  large 
numbers  around  all  the  watering-places,  and  the  cowboys  spent  much  of  their  time  in 
fastening  ropes  to  dead  animals  and  dragging  them  away  from  the  water.  Even  the  hardy 
antelope  among  the  mountains  suffered  just  as  did  the  cattle,  and  died  in  the  same  way 
around  the  watering-places. 

In  addition  to  the  two  ancient  villages  already  mentioned  there  appear  to  have  been 
four  others  in  the  entire  plain  of  the  Animas  Valley,  which  extends  40  miles  northward  from 
the  old  strand  to  the  railroad.  There  were  also  a  considerable  number  of  cliff  and  cave 
dwelhngs  in  the  mountains.  The  habitations  in  the  mountains  are  said  to  be  near  spots 
which  have  water  in  good  years,  although  many  of  them  are  absolutely  dry  for  periods  of 
over  a  year  at  a  time.  The  largest  villages  of  the  Hohokam  in  this  vicinity  were  located 
nearly  30  miles  from  the  old  lake  near  the  present  post-office  of  Animas.  Here,  at  three 
different  sites,  fire-places  and  pottery  are  found  scattered  among  old  mounds,  covered  in 
many  cases  with  sacaton  grass.  Formerly  stone  foundations  were  visible,  but  the  score 
or  more  of  settlers  who  have  lately  brought  their  families  hither  have  carried  them  away. 
The  number  of  inhabitants  must  have  been  considerable,  for  one  of  the  settlers  stated 
that  he  once  hauled  away  a  load  of  50  metate  stones  to  use  in  lining  a  well,  and  his  neighbors 
have  done  likewise.  The  Hohokam,  here  as  elsewhere,  were  a  distinctly  agricultural  people ; 
their  number,  if  the  ruins  are  a  safe  guide,  must  have  much  exceeded  that  of  the  present 


72 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


settlers.  The  present  settlers  agree  with  the  pig-rancher  already  quoted.  One,  who  has 
lived  in  the  country  27  years,  said  that  during  that  time  only  6  years  had  been  moist 
enough  so  that  a  crop  of  corn  could  be  raised  without  artificial  irrigation  by  water  pumped 
from  wells  in  the  spring.  A  bean-crop  might  have  been  made  oftener,  but  not  over  half 
the  time.  The  natural  flood  irrigation,  which  supports  the  sturdy  sacaton  grass  and  makes 
cattle-raising  feasible,  does  not  usually  reach  the  main  valley  until  mid-July,  too  late 
for  crops.  Kaffir  corn  and  milo  maize  do  better  than  Indian  corn,  but  they  are  of  httle  use 
except  for  stock,  and  they  were  unknown  to  the  Hohokam. 

Two  other  cases,  far  to  the  northeast  of  the  Animas  region,  may  be  briefly  described  as 
final  illustrations  of  the  Hohokam  villages.  The  Jarilla  Mountains  are  an  insignificant 
group  of  detached  hills  lying  in  the  center  of  southern  New  Mexico,  50  miles  north-northeast 
of  El  Paso  and  300  miles  east  of  Tucson.  Because  of  the  presence  of  copper  and  other 
metals,  a  small  mining  industry  grew  up  here  a  few  years  ago,  but  its  boom  is  over  and 
only  a  few  hopeful  prospectors  still  remain.  As  no  water  could  be  obtained  among  the 
mountains  the  El  Paso  and  Southwestern  Railroad,  now  a  part  of  the  Rock  Island  system, 
had  previously  been  forced  to  construct  a  pipe-fine  to  some  higher  mountains,  20  miles  to 
the  east.  Except  during  the  rainy  season,  when  water  is  stored  in  cisterns,  the  water 
thus  brought  has  formed  the  sole  supply,  not  only  for  the  railroad  itself  but  for  two  little 
mining  towns,  so  long  as  they  had  any  inhabitants.  So  far  as  I  could  learn,  only  two 
persons,  both  of  whom  combine  a  little  cattle-raising  with  the  enticing  but  unremunerative 
occupation  of  prospecting,  depend  on  any  other  water-supply.  These  two  men  five  far 
off  from  the  rest  of  mankind,  and  get  their  water  from  deep  wells  whose  construction  would 
be  utterly  beyond  the  capacity  of  primitive  people  without  iron  tools.  The  only  surface 
water  is  in  Water  Canyon,  but  the  name  is  a  misnomer.  The  settler  who  fives  there  was 
most  scornful  when  he  was  asked  about  the  “spring.”  He  said  there  was  no  spring,  only 
a  damp  spot  in  years  of  unusually  good  rainfall.  A  visit  to  the  place  confirmed  his  state¬ 
ment.  Nothing  was  to  be  seen  but  a  waterless  valley,  slightly  damp  because  rain  had  fallen 
the  day  before;  but  no  one  would  ever  suspect  the  presence  of  a  spring  except  from  the  traces 
of  an  old  path  and  of  an  Indian  encampment.  In  spite  of  the  present  absolutely  uninhabit¬ 
able  character  of  the  Jarilla  Mountains  for  any  people  not  able  to  dig  wells  or  construct 
large  cisterns  fined  with  mortar,  and  in  spite  of  the  fact  that  in  ordinary  years  no  crops 
can  now  be  raised  there  without  irrigation,  one  finds  the  remains  of  three  distinct  villages 
of  the  kind  already  described.  The  pottery  and  other  relics  of  man  are  not  so  thick  as  in 
the  large  villages  of  the  Santa  Cruz,  but  they  are  so  abundant  that  the  ground  is  thickly 
strewn  with  them.  No  one  of  the  villages  is  less  than  half  an  hour’s  walk  from  the  dry 
spring,  and  two  of  them  are  4  or  5  miles  away.  All  are  obviously  located  close  to 
land  which  could  be  cultivated  by  flood  irrigation  if  there  were  enough  water  and  if  the 
inhabitants  could  have  a  permanent  supply  to  drink. 

The  last  illustration  which  I  shall  put  forth  in  the  present  connection  is  located  on  the 
lonely  western  side  of  the  Otero  Basin,  not  far  from  the  western  shore  of  one  of  the  saline 
playas,  whence  the  gypsum  of  the  White  Sands  is  collected  by  the  wind.  Here,  in  a 
distance  of  30  miles  and  perhaps  much  more,  the  only  inhabited  place  in  1911  was  Beard’s 
Ranch,  where  a  sadly  diminished  stock  of  cattle  is  still  cared  for.  Four  and  a  half  miles 
north  of  the  ranch  two  good-sized  canyons,  named  Dead  Man  and  Lost  Man,  emerge  from 
the  San  Andreas  Mountains  and  together  form  a  great  fan  of  gravel  and  other  alluvium. 
At  the  lower  edge  of  this  the  traces  of  a  large  village  are  found.  The  ancient  village  covered 
an  area  about  half  a  mile  in  diameter,  thickly  inhabited  in  the  middle,  and  with  a  gradually 
decreasing  number  of  houses  toward  the  edges.  In  two  distinct  central  areas  pottery  is 
so  thickly  strewn  that  one  crushes  it  at  every  step;  in  places  it  is  literally  so  thick  that  it 
is  almost  impossible  to  put  one’s  foot  down  without  touching  it.  Much  of  the  pottery  is 
ordinary  coarse  red  ware,  but  there  is  a  great  deal  that  is  ornamented.  The  greater  part 


RUINS  IN  NORTHERN  SONORA  AND  SOUTHERN  NEW  MEXICO. 


73 


of  that  which  is  ornamented  is  painted  white  on  the  inside  and  is  decorated  with  black 
lines.  It  resembles  that  found  in  the  clilf  dwellings  and  other  villages  farther  to  the  north 
rather  than  that  of  the  villages  in  southern  Arizona.  Old  hearths  of  cobble-stones  set  in 
circles  2  feet  in  diameter  are  common,  and  in  the  center  of  the  village  are  only  50  to  100 
feet  apart,  which  seems  to  imply  a  dense  population.  Many  large  stones  are  scattered 
here  and  there  in  groups  among  the  houses,  but  are  not  now  in  any  definite  arrangement 
except  in  one  case,  where  they  form  part  of  a  circle  10  feet  in  diameter.  Many  of  the 
stones  have  been  broken  to  small  bits  by  the  action  of  the  frost,  which  would  seem  to  imply 
great  age.  The  same  implication  is  derived  from  the  high  degree  to  which  the  pottery  has 
been  broken  to  small  fragments,  and  also,  perhaps,  from  the  way  in  which  eolian  erosion 
has  scoured  the  ground  into  hollows  2  feet  or  more  in  depth. 

The  present  water-supply  at  this  place  is  almost  negative,  and  the  possibilities  of  agri¬ 
culture  are  still  smaller.  In  1909,  according  to  the  men  who  live  at  the  Beard  Ranch,  no 
water  at  all  flowed  past  this  place.  In  1910  a  little  came  down  two  or  three  times  for  an 
hour  or  two  during  the  heavy  summer  rains.  Even  in  years  of  good  rainfall  it  comes  only 
two  to  four  times,  and  never  for  more  than  an  hour  or  two  at  any  one  time.  The  slope 
here  is  fairly  pronounced,  and  the  soil  is  gravelly  and  porous,  so  that  reservoirs  could  only 
be  made  with  great  difficulty.  That  they  could  hold  water  for  two  years,  as  would  have 
been  necessary  from  the  summer  of  1908  to  that  of  1910,  seems  scarcely  possible.  The 
nearest  supply  of  water  at  any  time  of  year  except  during  showers  is  at  Hughes  Spring,  4 
miles  away  among  the  mountains.  Even  if  the  inhabitants  could  have  drunk  from  this, 
they  could  not  have  used  it  to  water  their  crops.  Indeed  it  is  impossible  to  see  how  they 
could  have  raised  crops  of  any  kind  or  in  even  the  smallest  quantity  under  the  present 
conditions.  To-day  not  only  do  the  settlers,  both  Americans  and  Mexicans,  make  no 
attempt  whatever  at  cultivation  without  irrigation,  but  many  of  the  cattlemen  have  been 
obliged  to  move  away  for  lack  of  rain. 

As  to  the  age  of  this  ruin  and  others,  there  is  little  direct  evidence.  At  the  Beard  village 
a  large  mesquite  bush,  with  roots  as  thick  as  a  man’s  thigh,  has  grown  up  in  the  very  midst 
of  an  old  stone  hearth.  The  bush,  according  to  Dr.  Forrest  Shreve,  of  the  Desert  Botanical 
Laboratory,  may  be  from  300  to  600  years  old.  Probably  an  equal  or  much  longer  time 
must  have  elapsed  after  the  abandonment  of  the  village  before  a  seed  could  take  root  and 
grow  in  such  a  disadvantageous  spot.  These  are  the  roughest  estimates,  and  merely  serve 
to  show  that  the  minimum  age  of  the  ruins  is  probably  well  toward  1,000  years,  while 
they  may  be  much  older. 

In  the  preceding  pages  a  great  number  of  facts  which  were  observed  in  Arizona,  Sonora, 
and  southern  New  Mexico  have  been  omitted,  not  because  they  are  not  conclusive,  but 
because  they  are  of  the  same  type  as  those  here  included.  I  have  endeavored  to  state  the 
facts  fairly  without  warping  them  to  suit  any  particular  theories.  It  remains  for  the 
reader  to  form  his  own  conclusions  as  to  whether  they  do  or  do  not  indicate  a  change  of 
climate.  In  considering  this  matter  it  must  be  remembered  that,  for  the  moment,  the 
choice  is  merely  between  the  occurrence  or  non-occurrence  of  changes;  the  question  of 
dates  and  periodicity  does  not  enter  into  the  matter.  So  far  as  probability  is  concerned, 
neither  theory  has  any  innate  advantage.  On  the  one  side  may  be  put  the  fact  that  the 
records  of  the  past  hundred  years  are  interpreted  by  meteorologists  to  mean  that  there 
has  been  no  change  during  that  period.  On  the  other  hand  stands  the  fact  that  since  the 
culmination  of  the  glacial  period,  presumably  about  30,000  years  ago,  tremendous  changes 
are  universally  agreed  to  have  taken  place.  During  the  last  century  the  slight  changes 
which  have  taken  place  from  decade  to  decade  have  sufficed  to  produce  important  effects 
upon  agriculture,  and  to  drive  out  settlers  from  dry  regions,  after  tempting  them  in  during 
wet  times.  This,  however,  has  been  on  a  scale  far  smaller  than  that  which  is  applicable 
to  the  ruins.  If  we  accept  the  hypothesis  of  no  change,  we  must  adopt  the  assumption  that 


74 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  Hohokam  possessed  a  degree  of  mobility  vastly  in  excess  of  that  of  any  other  known 
people  of  similar  agricultural  habits.  We  must  also  believe  that  whereas,  during  the  past 
200  years,  the  modern  Zunis,  who  are  often  quoted  in  this  connection,  have  abandoned 
two  villages,  one  of  which  is  now  being  reoccupied,  the  Hohokam  abandoned  their  villages 
by  the  hundi’ed  without  assignable  cause.  We  must  further  assume  that  all  the  apparent 
indications  of  a  formerly  dense  population  are  utterly  misleading.  The  Hohokam  lived 
here  to-day  and  there  to-morrow.  Somehow  they  knew  when  the  rains  would  be  propitious : 
therefore  they  abandoned  the  sites  where  water  is  always  abundant,  and  went  far  out  into 
the  wastes  to  sites  which  have  water  only  in  the  most  favorable  years  and  where  agriculture 
is  now  remunerative  only  about  one  year  in  five. 

If  we  accept  the  alternative  theory,  no  assumptions  are  required.  The  Hohokam  acted 
like  other  races;  they  lived  where  there  was  an  opportunity  to  obtain  food  by  agriculture. 
When  the  rainfall  diminished  they  starved,  or  else  were  driven  out  by  enemies  who  them¬ 
selves  were  set  in  motion  by  hunger.  In  the  early  times,  when  rainfall  was  abundant,  they 
dwelt  in  peace  and  comfort;  when  evil  days  cut  down  the  supply  of  water  and  of  food, 
war  and  misery  sprang  up.  The  dwellers  in  the  villages  of  less  favorable  location  were 
driven  into  hunger  and  despair,  and  took  to  plundering,  robbing,  and  raiding.  Thus  of 
necessity  the  art  of  defense  was  greatly  stimulated  among  those  who  dwelt  in  the  more 
desirable  regions ;  and  we  find  the  best  forts  not  in  the  regions  at  the  lower  ends  of  the  rivers, 
but  far  upstream,  where  the  dwindling  Hohokam  made  their  final  stand.  We  might  go 
on  to  show  in  a  score  of  ways  how  one  theory  demands  large  assumptions,  while  the  other 
demands  none  whatever.  The  weight  of  probability  seems  to  lie  on  the  side  of  changes 
in  climate.  We  shall  go  on  to  see  how  and  when  these  changes  may  have  occurred. 


CHAPTER  IX. 


THE  SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 

The  ruins  of  southern  Arizona  and  the  neighboring  parts  of  New  Mexico  and  Sonora 
by  no  means  exhaust  the  evidence  bearing  on  changes  of  climate.  It  is  advisable  to  present 
further  evidence  for  several  reasons.  In  the  first  place  the  examination  of  numerous  ruins 
in  the  northern  half  of  New  Mexico  on  the  one  hand,  and  in  Central  America  and  the  south¬ 
ern  part  of  old  Mexico  on  the  other,  shows  how  widely  the  phenomena  of  climatic  change 
appear  to  extend.  In  the  second  place  such  an  examination  brings  out  the  fact  that  civiliza¬ 
tions  of  quite  diverse  types  were  similarly  affected.  Moreover,  it  suggests  that  the  rise  and 
fall  of  civilization  in  America  have  been  marked  by  a  periodic  or  pulsatory  character  similar 
to  that  of  the  Old  World  and  perhaps  connected  in  some  way  with  variations  in  climate. 
And  finally,  in  the  case  of  Yucatan,  it  brings  out  something  of  the  probable  nature  of  the 
changes  with  which  we  have  to  deal.  In  the  present  chapter  I  shall  discuss  some  of  the 
ruins  of  the  northern  half  of  New  Mexico,  leaving  those  of  old  Mexico  and  Central  America 
for  later  consideration.  Three  regions  will  be  taken  up,  not  because  they  are  more  remark¬ 
able  than  many  others,  but  because  those  particular  ones  happened  to  be  suggested  as  likely 
to  prove  good  places  for  study,  and  because  they  admirably  illustrate  the  various  stages  of 
culture  in  the  northern  part  of  the  area  where  relatively  high  civilization  prevailed  in  early 
America.  One  of  the  regions  is  the  Chaco  Canyon  on  the  edge  of  the  Navajo  Reservation 
in  the  northwest  corner  of  New  Mexico;  another  is  the  Pajaritan  Plateau  in  the  northern 
part  of  the  State,  a  little  northwest  of  Sante  Fe;  the  third  is  the  district  of  Gran  Quivira, 
in  the  center  of  the  State,  south  of  Willard. 

Chaco  Canyon,  which  lies  85  miles  from  the  northern  or  Colorado  boundary  of  New 
Mexico,  and  75  miles  from  the  western  boundary  toward  Arizona,  is  situated  in  the 
center  of  one  of  the  most  interesting  regions  in  North  America.  Its  bare,  bright-colored 
mesas,  wooded  mountain  tops,  broad  desert  plateaus,  and  steep-sided,  inaccessible  canyons 
have  a  unique  and  striking  quality  which  impresses  itself  upon  the  memory.  It  is  sur¬ 
rounded  by  the  most  noteworthy  ruins  to  be  found  in  any  part  of  the  United  States.  To 
the  north,  for  instance,  at  a  distance  of  115  miles,  the  famous  Cliff  Dwellings  of  Mancos 
never  fail  to  arouse  the  enthusiasm  of  the  visitor,  even  though  he  be  wholly  ignorant  of 
archeology.  Only  65  miles  west  of  Chaco  Canyon  the  innumerable  ruins  of  the  Canyon  de 
Chelly  speak  of  a  past  full  of  busy  life  and  activity  and  characterized  by  a  considerable 
degree  of  inventiveness  and  no  mean  amount  of  accomplishment  in  view  of  the  oppor¬ 
tunities.  On  the  other  side,  eastward,  the  whole  country  is  full  of  ruins,  some  of  which 
will  be  discussed  when  we  come  to  speak  of  the  Pajaritan  Plateau,  100  miles  away. 

The  present  inhabitants  of  the  district  surrounding  the  Chaco  Canyon  are  no  less 
interesting  than  the  scenery  and  the  ruins.  To  the  southwest,  at  a  distance  of  80  miles, 
the  modern  Zunis  are  one  of  the  few  ancient  tribes  which  still  dwell  in  the  land  and  perhaps 
preserve  some  connection  between  the  past  civihzation  and  that  of  the  present.  At 
Oraibi,  130  miles  to  the  west,  the  Hopi  tribe  is  perhaps  even  more  interesting  as  a  diminished 
remnant  of  a  state  of  culture  wholly  different  from  that  prevalent  in  most  parts  of  the 
Southwest  at  the  time  of  the  arrival  of  the  Spaniards.  Toward  the  east  and  southeast, 
at  distances  of  100  miles  more  or  less,  the  Pueblo  Indians  are  a  third  type  of  ancient  people, 
less  archaic  than  the  others,  but  vastly  different  from  anything  elsewhere  in  the  United 

75 


76 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


States.  Surrounded  by  these  three  tribes  the  Navajos  live  in  the  country  near  Chaco 
Canyon,  not  dwelling  in  villages  because  the  country  is  too  dry  to  permit  agriculture, 
nor  yet  plundering  after  the  manner  of  their  fathers  because  of  the  restraining  hand  of  the 
white  man,  but  caring  for  sheep  and  living  a  life  almost  identical  with  that  of  the  nomads 
in  Persia  or  similar  parts  of  Asia. 

Chaco  Canyon  may  be  reached  either  by  wagon  from  Gallup  on  the  Santa  Fe  Railroad 
or  by  a  shorter  horseback  ride  of  55  miles  straight  north  from  the  station  of  Thoreau.  On 
the  way  from  Thoreau  one  passes  through  five  distinct  groups  of  ruins,  including  those 
at  the  destination.  How  great  the  actual  number  of  ruins  may  be  I  can  not  say,  for  I 
could  not  procure  a  guide  and  was  obliged  to  ride  alone,  turning  aside  only  where  I  had  been 
especially  informed  of  the  existence  of  something  worth  seeing.  Nevertheless  I  saw  liter¬ 
ally  scores  of  one  size  or  another.  Of  modern  places  of  habitation,  on  the  contrary,  I  did 
not  see  over  twenty,  although  I  went  by  one  road  and  returned  by  another.  One  of  the 
places  of  habitation  was  a  newly  established  Indian  agency;  three  were  the  homes  of  white 
men  whose  sole  business  is  trading  with  the  Indians;  two  were  the  ranches  of  white  men 
who  trade  with  the  Indians  and  also  raise  sheep  in  one  case  and  cattle  in  the  other;  the 
rest  were  the  temporary  tents  of  nomadic  Navajos,  who  camp  here  and  there  with  their 
sheep. 

Let  us  turn  now  to  a  description  of  the  ruins  seen  on  the  ride  from  Thoreau  to  Chaco 
Canyon.  Thoreau,  with  its  saloon,  hotel,  store,  and  one  or  two  dwelling-houses,  is  a 
typical  little  railroad  station  in  the  lofty  plateau  region  of  northwestern  New  Mexico  and 
northern  Arizona.  Lying  at  an  altitude  of  nearly  7,000  feet,  and  exposed  to  the  unclouded 
rays  of  the  sun  at  all  times  of  the  year,  it  is  warm  by  day  even  in  winter,  and  cool  by  night 
even  in  midsummer.  The  wooded  Zuni  Mountains  rise  a  few  miles  to  the  south,  and  sup¬ 
port  a  lumber  industry  which  is  the  chief  excuse  for  Thoreau’s  existence.  On  the  other 
side,  northward,  the  plain  is  bordered  by  a  line  of  magnificent  red  cliffs  which  rise  1,000 
feet  more  or  less,  and  run  for  miles  parallel  to  the  railroad.  Riding  eastward  at  the  foot 
of  these  one  traverses  a  barren  plain  without  vestige  of  modern  habitation.  No  water  is 
to  be  found  here  for  many  miles  except  along  the  railroad  where  wells  have  been  dug. 
Even  there  it  is  so  brackish  that  the  few  people  who  live  at  each  station  prefer  to  buy 
water  brought  by  train  rather  than  to  drink  that  of  the  wells.  If  it  were  not  for  the  railroad 
no  one  would  live  in  the  country  except  a  few  nomadic  Navajos,  wandering  hither  and 
thither  with  their  sheep,  according  to  where  scanty  grass  or  a  little  water  are  to  be  found. 
In  spite  of  its  proximity  to  the  railroad,  this  is  one  of  the  most  sparsely  inhabited  regions 
in  the  whole  United  States.  Yet  as  soon  as  one  approaches  the  base  of  the  great  red  cliffs 
pottery  begins  to  appear  strewn  thickly  in  small  patches  among  low  mounds  which  are 
evidently  the  much  weathered  and  battered  remnants  of  small  communal  houses  scattered 
here  and  there  at  intervals  of  a  few  hundred  yards.  How  many  such  mounds  there  may 
be  I  can  not  tell,  for  after  riding  among  them  for  a  mile  and  a  half  I  turned  northward  up 
Chaves  Canyon  into  the  heart  of  the  red  mountains.  The  ruins  are  located  close  to  the 
mouth  of  small  mountain  valleys  where  the  floods  from  summer  storms  spread  out,  and 
where  the  soil  is  of  the  sandy  type  best  adapted  to  cultivation  in  so  dry  a  region.  Agri¬ 
culture  would  readily  be  possible,  provided  only  there  were  an  assurance  of  flood-water 
sufficient  to  support  the  crops  every  year  instead  of  only  in  good  years. 

The  next  4  miles  of  the  road  lead  up  the  narrow  valley  of  Chaves  Canyon  where  there 
is  no  room  for  agriculture.  Then  the  trail  comes  out  upon  an  upland  stretch  8  or  9  miles 
wide  between  the  divide  at  the  head  of  Chaves  Canyon  (7,150  feet  above  the  sea)  and  the 
main  continental  divide  (100  feet  higher)  at  the  head  of  Satan’s  Canyon.  Most  of  the 
drainage  here  runs  centripetally  toward  the  shallow,  temporary  sheet  of  water  known  as 
Smith’s  Lake,  at  an  altitude  of  about  6,900  feet.  Much  of  the  land  is  rocky,  especially 
near  the  divides,  and  the  rest  is  less  sandy  and  thus  less  propitious  than  in  the  region  at 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


77 


the  base  of  the  cliffs.  Nevertheless  there  are  several  hollows  into  which  flood  water  flows 
and  where  flelds  of  corn  are  rudely  fenced  off  by  the  Navajos.  No  one  except  a  white 
trader,  however,  hves  here  permanently,  which  is  not  surprising,  since  the  total  area  of 
the  flelds  within  sight  of  the  road  is  probably  not  more  than  30  acres.  Yet  here,  as  in  so 
many  other  places,  the  people  of  long  ago  were  fairly  numerous.  Without  deviating  from 
the  road  one  passes  ruins  in  four  places,  the  total  number  of  houses  being  about  10  and  of 
rooms  70,  which  would  provide  accommodation  for  about  50  people.  These  houses  were  of 
a  different  sort  from  those  that  we  have  investigated  in  the  south.  They  were  communal 
dwellings  made  of  rough  stones  and  probably  plastered  with  mud,  but  now  reduced  to  low 
and  almost  invisible  mounds.  To-day  the  only  permanent  supply  of  water  is  in  Smith’s 
well,  12  feet  deep.  The  lake  often  dries  up  for  six  months  at  a  time,  and  any  reservoirs  that 
the  former  inhabitants  could  have  built  would  scarcely  have  been  more  permanent.  The 
ruins  are  too  small  to  prove  anything  when  taken  by  themselves.  They  are  worth  men¬ 
tioning  simply  because  they  show  how  numerous  are  the  traces  of  ancient  habitations  and 
because  they  bear  so  marked  an  appearance  of  great  age. 

North  or  northwest  of  the  continental  divide  a  large  number  of  valleys  break  through 
the  white  and  brown  chffs,  which  correspond  to  the  red  chffs  of  the  southern  side,  and 
debouche  upon  a  vast  rolhng  plateau  hke  that  upon  which  Thoreau  is  located.  Here,  just 
as  on  the  other  side,  the  mouth  of  each  canyon  forms  a  center  around  which  clusters  a  group 
of  ruins.  For  instance,  at  the  mouth  of  Satan’s  Canyon,  down  which  runs  the  road  to  the 
main  center  of  Chaco  Canyon  at  Pueblo  Bonita,  the  most  prominent  feature  of  the  monot¬ 
onous  landscape,  as  one  looks  out  from  the  mouth  of  the  valley,  is  the  circular  stone  tower  of 
Pueblo  Viejo  or  Kin  Ya’a,  30  feet  high  and  15  in  diameter.  Four  stories  can  still  be  counted 
in  it,  and  not  many  years  ago  there  are  said  to  have  been  five,  although  the  upper  parts 
have  now  fallen.  The  tower  rises  from  a  stone  fort  or  sanctuary,  about  150  by  80  feet  in 
size.  The  whole  structure  is  built  of  blocks  of  brown  sandstone  which  have  been  broken 
and  smoothed  with  surprising  accuracy,  considering  that  the  ancient  inhabitants  did  not 
possess  metal  tools.  All  the  stone  must  have  been  brought  from  the  mountains  on  the 
backs  of  men  or  women,  no  slight  task  considering  that  some  of  the  blocks  are  4  feet  long, 
1  foot  wide,  and  6  or  8  inches  thick,  and  must  weigh  300  to  400  pounds.  Aside  from  the 
circular  tower  the  fort  contains  21  rooms  which  are  still  distinct;  these  are  much  larger 
than  the  rooms  of  ordinary  dwelHng-houses,  and  vary  from  10  by  12  to  20  by  30  feet. 
Probably  the  larger  ones  were  never  covered  with  roofs.  We  can  not  be  sure  of  this, 
however,  for  the  ancient  people  knew  how  to  utilize  wooden  beams,  as  is  evident  in  the 
tower,  where  the  different  stories  appear  to  have  been  separated  by  floors  built  of  wood. 
Apparently  the  inhabitants  did  not  for  the  most  part  dwell  in  the  fort  itself,  but  in  less 
pretentious  and  more  extensive  structures  round  about.  These  are  now  reduced  to  long 
rounded  mounds  of  varying  height.  Evidently  some  parts  had  one  story,  some  two,  and 
some  probably  three.  They  were  built  of  stones  like  the  fort,  but  with  less  care  and  with 
smaller  blocks  less  painstakingly  squared.  Within  a  radius  of  a  quarter  of  a  mile  of  the 
fort  eleven  communal  dwelling-houses  can  be  counted.  Reckoning  the  average  size  of 
the  rooms  as  9  by  10  feet,  which  is  the  approximate  size  of  those  excavated  in  similar  ruins, 
and  allowing  for  some  parts  having  two  stories  and  a  few  three,  the  total  number  of  rooms 
in  this  village  was  probably  over  300,  or  enough  for  a  population  of  250  people. 

Kin  Ya’a  is  not  the  only  ruin  in  this  immediate  vicinity.  About  a  third  of  a  mile  to  the 
west  another  and  larger  one,  nameless  so  far  as  I  could  ascertain,  has  an  extent  of  at  least 
800  feet  from  north  to  south.  It  appears  to  have  been  composed  of  a  number  of  large 
communal  houses,  built  close  together.  Most  of  the  houses  were  apparently  one  story 
high,  and  were  constructed  without  much  stone.  At  the  south  end  of  the  village,  however, 
there  was  a  large  house,  90  feet  long,  having  at  least  two  stories  and  possibly  three.  Half 
a  mile  north  of  Kin  Ya’a,  still  a  third  ruin  has  three  or  four  houses  and  possibly  100  rooms. 


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THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Whether  any  more  ruins  exist  at  the  mouth  of  this  particular  valley  is  not  certain,  but 
probably  others  could  be  found.  The  next  valley  to  the  west  is  a  small  one,  yet  at  its 
mouth  the  usual  series  of  ruins  is  found.  I  saw  two,  both  of  them  being  groups  of  small 
low  mounds  where  a  few  famihes  had  gathered  stones  to  build  their  little  hamlets  and 
utilize  the  waters  during  the  period  of  floods.  Still  farther  west  lies  the  valley  in  which 
the  Indian  agency  is  located.  Here  small  ruins  having  six  or  seven  houses  occur  in  three 
places.  The  Indian  traders  and  the  one  white  sheep-rancher  in  the  neighborhood  say  that 
this  valley  and  its  neighbor  on  the  east  contain  other  ruins  which  I  did  not  see. 

Westward  from  the  agency  a  number  of  other  valleys  debouche  from  the  mountains, 
but  I  had  no  time  to  examine  them.  In  one  of  these,  Indian  Creek,  8  miles  from  the 
agency,  there  lives  an  Indian  trader,  Dalton  by  name,  who  has  been  in  the  country  many 
years.  Within  a  mile  of  his  store,  either  up  or  down  the  dry  bed  of  Indian  Creek,  he  states 
that  there  are  15  to  20  small  ruins  of  from  one  to  six  or  eight  rooms.  Apparently  the 
former  population  was  large  compared  with  that  of  to-day.  Some  of  the  ancient  people 
seem  to  have  left  their  habitations  much  earher  than  others,  the  small  ruins  in  the  minor 
valleys  having  been  abandoned  long  before  the  large  ones  in  the  valleys  of  greater  size, 
such  as  Satan’s  Canyon.  In  some  cases  drinking  water  can  now  be  procured  by  going  a 
long  distance  to  springs;  in  other  cases  one  can  not  see  where  it  was  obtained.  This, 
however,  may  be  neglected  while  we  turn  our  attention  to  the  way  in  which  the  people 
procured  a  livelihood. 

The  people  in  this  part  of  New  Mexico,  like  the  Hohokam  of  the  south,  were  preemi¬ 
nently  agricultural,  and  must  have  obtained  practically  their  whole  living  from  the  soil. 
That  they  hved  in  one  place  permanently  is  clear,  not  only  from  arguments  like  those  used 
in  connection  with  earlier  ruins,  but  from  the  large  size  of  their  fort  and  from  the  great 
amount  of  work  which  they  lavished  on  its  construction.  How  numerous  they  were  we 
can  not  say  with  certainty,  but  at  the  mouth  of  Satan’s  Canyon  it  scarcely  seems  as  if 
there  could  have  been  less  than  500  or  600  people.  The  next  valley  may  have  had  20; 
the  next  (in  which  the  agency  is  located)  25,  and  so  on.  In  a  stretch  of  16  miles  from 
Satan’s  Canyon  westward  past  the  agency  and  Dalton’s,  there  must  be  at  least  a  dozen 
valleys,  and  the  whole  number  of  people  probably  mounted  well  up  toward  800  or  more. 
At  present  the  Navajos  cultivate  as  much  land  as  they  can,  although  they  do  it  carelessly 
because  the  crops  so  often  fail.  In  the  16  miles  under  discussion,  there  are  now  only  two 
families,  according  to  Mr.  Dalton,  who  raise  corn  enough  actually  to  support  themselves 
through  the  entire  year.  The  rest  depend  upon  their  flocks  and  buy  corn  from  outside 
sources.  The  whole  number  of  famihes  who  own  cultivable  land  amounts  to  only  25, 
he  says,  and  the  total  amount  of  land  is  only  65  acres,  or  suflicient  to  support  33  people 
according  to  our  Arizona  estimate.  Mr.  Dalton,  however,  thinks  that  the  number  would 
be  less  than  this,  for  he  says  that  the  famihes  who  actually  carry  on  cultivation  do  not 
raise  more  than  one-tenth  enough  to  support  themselves,  supposing  that  they  had  to 
depend  on  what  they  could  raise  and  not  on  sheep.  Judging  from  the  poor  appearance 
of  the  crops,  and  the  frequency  with  which  they  fail,  he  is  probably  not  far  from  right. 

The  plateau  extending  northward  from  the  base  of  the  chffs  where  the  ruins  just  de¬ 
scribed  are  located  is  a  desolate  region,  with  no  inhabitants  save  occasional  wandering 
Navajo  and  one  or  two  traders  and  sheep-men.  It  is  now  absolutely  devoid  of  cultivation; 
nevertheless,  it  has  a  few  ruins,  which  form  the  fourth  of  our  five  groups.  Some  of  these 
are  small,  insignificant  mounds,  almost  invisible,  and  apparently  very  old.  Human  bones 
and  complete  skeletons  facing  the  east,  and  with  jars  or  shallow  bowls  on  their  breasts,  are 
often  found  near  them,  and  it  was  clearly  the  custom  of  the  inhabitants  to  bury  their 
dead  close  to  the  villages.  This  is  quite  different  from  the  habits  of  the  builders  of  the 
larger  and  apparently  later  villages,  for  their  burials  are  rarely  found  and  seem  never  to  be 
near  the  villages.  Seemingly,  as  Bandelier  long  ago  pointed  out,  we  have  two  types  of 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


79 


civilization,  an  older  and  more  widespread  one  dwelling  in  small  hamlets  far  remote  from 
present  sources  of  water,  and  a  later  one  clustering  nearer  the  sources  of  water  and  building 
large,  well-protected  villages. 

The  second  or  later  type  of  ruins  has  already  been  illustrated  by  the  castle  of  Kin  Ya’a 
or  Pueblo  Viejo.  A  much  more  remarkable  illustration,  however,  is  found  in  the  notable 
ruins  of  Chaco  Canyon.  This  is  a  steep-sided,  flat-floored  valley  cut  in  the  plateau  25 
or  30  miles  north  of  the  cliffs  at  the  northern  base  of  the  Continental  divide.  The  ruins 
center  around  Pueblo  Bonita,  the  home  of  a  trader,  and  the  only  permanently  inhabited 
place  for  many  miles.  Within  half  a  mile  or  less  of  this  place  there  are  six  large  ruins  and 
at  least  ten  small  “suburban”  ones.  Farther  away  there  are  others  scattered  up  and 
down  along  the  canyon  and  in  the  lower  parts  of  the  chief  tributary  valleys.  Most  of  the 
ruins  are  on  the  valley  floor,  but  a  considerable  number  are  high  on  the  level  plateau,  far 
above  the  bottoms  of  the  valleys.  None  of  the  larger  ones,  however,  appears  to  be  at  a  great 
distance  from  the  main  lines  of  drainage,  or  from  places  where  a  supply  of  drinking-water 
might  be  secured  with  a  moderate  amount  of  care  in  the  construction  of  reservoirs.  Often 
a  considerable  climb  would  be  required  to  surmount  the  high  cliffs  and  carry  the  water  up 
from  the  stream,  but  that  would  not  be  of  great  importance  among  a  primitive  people. 

The  ruins  in  this  region,  more  than  in  any  other  that  we  have  yet  discussed,  present  an 
appearance  of  solidity  and  permanence.  (Plate  3,  b.)  This  does  not  mean  that  they  were 
necessarily  occupied  more  permanently  or  even  as  much  so  as  the  others,  but  being  built 
of  stone  they  are  massive  and  durable,  and  have  withstood  the  ravages  of  time.  Moreover, 
they  appear  to  be  younger  than  at  least  a  part  of  those  which  we  have  been  considering. 
The  larger  ruins  are  strongly  built,  compact  structures  with  lofty  stone  walls,  sohd  at  the 
base,  but  sometimes  pierced  with  windows  at  the  level  of  the  upper  stories.  Each  one  must 
have  sheltered  several  hundred  people,  as  appears  not  only  from  their  size,  but  from  the 
amount  of  labor  required  in  building  them.  The  largest  are  thought  by  some  students  to 
have  had  as  many  as  1,000  to  2,000  denizens.  It  must  have  taken  a  good  many  people  and 
a  long  occupation  to  build  a  large  number  of  villages  all  located  close  to  one  another,  and 
all  together  presenting  an  appearance  which  seems  quite  massive  even  to  the  modern 
traveler  accustomed  to  the  great  cities  of  the  present  and  to  the  ruins  of  the  most  famous 
empires  of  the  past.  The  permanence  of  the  villages  is  still  more  evident  when  we  consider 
the  amount  of  labor  involved.  We  must  constantly  bear  in  mind  that  the  American 
aborigines  not  only  had  no  iron  tools,  but  were  also  not  blessed  with  beasts  of  burden.  Yet 
all  the  stone  for  the  main  ruins,  such  as  Pueblo  Bonita  itself,  appears  to  have  been  brought 
from  a  considerable  distance,  a  mile  and  a  half,  so  it  is  said,  in  this  case.  The  trail  can  still 
be  seen  along  which  the  rock  was  brought  to  the  top  of  the  cliffs  to  be  thrown  down  to  the 
place  where  it  was  needed.  A  few  unused  rocks  still  lie  at  the  top  of  the  cliffs.  Of  course 
it  is  possible  that  certain  villages  were  built  and  immediately  abandoned  according  to  the 
frequent  assumption  of  archeologists  and  ethnologists,  but  this  seems  improbable,  for  people 
would  scarcely  go  to  so  much  labor  again  and  again  if  they  expected  soon  to  move  away. 
Moreover,  they  could  not  have  accomplished  all  that  the  ruins  still  show,  unless  they 
had  lived  in  the  place  many  years.  This  is  important  because  it  means  that  in  this  one 
limited  valley  or  its  environs  a  rather  dense  population,  numbering  probably  several 
thousand  people,  had  to  be  supported  year  after  year,  in  good  times  and  bad.  So  dense  a 
population  would  drive  out  all  the  game  in  a  short  time  and  could  not  depend  upon  that 
source  for  food;  nor  could  they  have  Hved  upon  wild  products,  for  there  are  none  that  would 
support  more  than  about  one  man  for  every  square  mile.  Therefore  all  these  people  must, 
it  would  seem,  have  been  dependent  upon  agriculture,  a  conclusion  by  no  means  new,  but 
which  means  much  when  considered  in  reference  to  climatic  changes  and  their  effects. 

The  problems  of  agriculture,  of  water-supply,  and  of  the  location  of  villages  are  all 
closely  connected.  We  have  just  seen  that  while  the  small  and  apparently  ancient  type 


80 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  ruins  may  be  located  far  away  from  any  visible  supply  of  water,  the  larger,  more  compact, 
and  apparently  later  ruins  are  always  located  fairly  near  to  a  permanent  source  of  drinking 
water.  Nevertheless,  water  was  evidently  not  the  only  desideratum  in  choosing  the  sites 
of  many  villages.  Pueblo  Alto,  near  Pueblo  Bonita,  lies  on  the  plateau  high  above  the 
valley  on  the  north  side,  while  the  ruin  of  Hermoso  hes  in  a  similar  situation  on  the  other 
side  of  the  canyon.  There  are  traces  of  an  ancient  spring  about  half  a  mile  from  Hermoso, 
but  it  is  dry  now  and  has  been  for  an  unknown  period.  As  for  Pueblo  Alto,  unless  the 
inhabitants  chmbed  down  the  chffs  they  can  have  obtained  water  only  from  small  reservoirs. 
In  dry  seasons,  even  with  a  considerably  greater  rainfall  than  now,  both  villages  would 
probably  have  had  to  send  their  women  down  to  the  main  canyon  for  water;  clearly  they 
were  not  located  with  any  reference  to  ease  in  obtaining  water.  Nor  were  their  situations 
easy  of  defense.  Both  Pueblo  Alto  and  Hermoso  are  on  the  nearly  smooth  plateau  in  places 
of  no  special  strategic  strength.  To  be  sure  they  are  more  or  less  completely  surrounded 
by  cliffs  that  can  be  scaled  only  with  difficulty,  but  the  cliffs  are  far  away  from  the  houses, 
and  no  attempt  has  been  made  to  locate  the  villages  in  places  surrounded  and  protected 
by  natural  barriers.  The  upland  villages  are  removed  from  the  main  line  of  easy  travel, 
but  otherwise  are  not  much  more  protected  from  sudden  raids  than  are  their  neighbors  in 
the  valley.  They  have  left  their  own  record  of  the  fact  that,  at  least  in  their  later  days, 
they  were  harassed  by  enemies.  The  record  takes  the  form  of  long  walls  which  sometimes 
jut  out  half  a  mile  from  a  village,  apparently  to  furnish  a  shelter  behind  which  to  flee  to 
the  village  in  case  of  attack.  Other  evidences  of  the  fear  of  enemies  are  found  in  circular 
shelters  of  stones,  placed  upon  conunanding  hilltops  or  upon  less  noticeable  elevations. 
Yet  the  villages  themselves  are  not  placed  in  sheltered  spots  but  merely  on  some  slight 
eminence  in  the  midst  of  the  generally  level  plateau.  If,  then,  the  plateau  villages  were 
not  located  with  special  reference  to  the  most  permanent  water-supply,  nor  in  the  places 
most  easily  defensible,  what  was  the  determining  factor  in  their  location?  The  answer 
seems  to  be,  “arable  land.”  If  the  population  was  as  great  as  we  have  inferred,  the  flat 
land  of  the  valley  bottom  must  have  been  inadequate  to  support  so  large  a  number  of 
people,  even  if  it  could  all  be  used.  The  choice  apparently  lay  between  putting  the  village 
in  the  main  valley  and  climbing  up  the  cliffs  to  reach  the  flelds,  on  the  one  hand,  or  placing 
the  village  on  the  plateau  and  chmbing  down  to  the  canyon  for  water,  on  the  other  hand. 
Some  chose  one  way  and  some  the  other,  but  probably  those  who  chose  the  valley  fared 
best  in  the  long  run.  If  the  climate  became  drier,  the  upland  fields  might  have  to  be 
abandoned,  but  those  in  the  vaUey  bottom  could  still  be  cultivated.  Moreover,  a  decreasing 
supply  of  water  would  not  occasion  them  more  work  in  order  to  get  enough  to  drink, 
whereas  the  necessity  of  descending  to  the  valley  for  water  in  dry  seasons  would  become  a 
distinct  tax  upon  their  lofty  neighbors.  Finally,  the  people  up  above,  being  already 
impoverished,  would  be  especially  subject  to  irreparable  injury  in  the  raids  of  enemies, 
and  so  not  only  would  have  to  build  works  of  defense,  but  would  perhaps  be  killed  off, 
forced  to  migrate,  or  impelled  to  take  to  plundering  on  their  own  account.  So  long  as 
the  rainfall  sufficed  to  render  cultivation  possible  upon  the  plateaus,  the  villages  there  had 
a  reason  for  existence.  If  present  conditions  prevailed  when  they  were  built,  their  dry, 
exposed  location  is  difficult  to  explain. 

After  all  that  has  been  said,  it  may  seem  almost  superfluous  to  speak  further  of  the 
inadequacy  of  the  present  agricultural  resources  of  the  Chaco  region,  yet  it  is  necessary 
because  scientific  writers  have  so  largely  maintained  that  the  present  water-supply  is 
adequate  for  as  large  a  population  as  ever  at  any  time  dwelt  here.  Oddly  enough,  the 
majority  of  thoughtful,  non-scientific  observers  who  have  lived  or  traveled  extensively 
in  New  Mexico  have  largely  been  of  the  opposite  opinion  and  have  agreed  with  Presi¬ 
dent  E.  McQ.  Gray,  of  the  University  of  New  Mexico,  who,  when  asked  his  idea  as  to 
the  conditions  prevailing  in  pre-Columbian  times,  remarked:  “I  never  thought  of  enter- 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


81 


taining  any  other  view  than  that  the  change  in  the  territory  was  due  to  a  change  in  the 
water-supply.” 

In  order  to  assist  in  a  final  settlement  of  this  question,  if  such  a  thing  be  possible,  let 
us  consider  the  present  conditions  of  agriculture  in  the  once  populous  Chaco  Canyon, 
There  are  now  in  the  canyon  two  Indians  who  are  reasonably  sure  of  a  good  crop  of  corn 
each  year.  I  saw  their  farms,  unbelievably  dreary  wastes  of  drifting  sand  in  the  bottom 
of  the  canyon  where  two  large  tributaries  join  and  where  the  level  of  ground  water  is 
consequently  higher  than  anywhere  else.  In  the  vicinity  of  the  chief  ruins,  2  or  3  miles 
upstream,  the  level  of  ground  water  is  20  feet  below  the  surface  of  the  lowest  part  of  the 
valley,  but  at  the  farms  water  can  always  be  secured  close  to  the  surface,  although  farther 
downstream  the  level  again  declines.  The  abundance  of  sand,  as  well  as  the  high  level  of 
ground  water,  is  also  helpful,  since  the  sand,  by  acting  as  a  mulch  to  prevent  the  evaporation 
of  the  ground  water,  is  an  extremely  useful  adjunct  of  agriculture.  In  spite  of  these  ad¬ 
vantages  neither  of  the  two  Indian  farmers  has  obtained  a  good  crop  every  year  in  recent 
times,  although,  according  to  the  local  story,  one  of  them  failed  only  because  he  did  not 
build  the  necessary  dam  to  retain  all  the  water  in  an  extremely  dry  year;  the  other  failed 
because  of  the  absolute  lack  of  water.  Various  other  Indians  cultivate  parts  of  the  valley 
floor,  but  with  the  most  meager  success.  In  good  years  the  corn  is  said  to  grow  to  a  height 
of  6  to  7  feet;  in  other  years  it  is  only  2  or  3  feet  high,  and  often  it  fails  completely. 

In  the  last  sixteen  years,  according  to  Mrs.  Wetherell,  the  wife  of  a  trader  whose  husband 
was  killed  by  the  Indians,  there  have  been  only  two  good  crops.  In  three  years,  1902, 1903, 
and  1904,  the  Navajos  planted  corn  as  usual,  but,  with  the  exception  of  the  two  fortunate 
men  aheady  mentioned,  got  no  returns.  In  the  remaining  years  the  crop  varied  all  the 
way  from  almost  nothing  to  fair.  The  reason  for  its  failure  in  the  dry  years  does  not  appear 
to  be  that  the  method  of  cultivation  is  poorer  than  in  the  past,  but  simply  that  the  summer 
rains,  upon  which  corn  and  beans  (the  only  possible  crops  among  the  aborigines)  entirely 
depend,  never  fell  at  all  or  else  did  not  fall  until  so  late  that  the  frost  came  before  the 
crops  could  ripen. 

Modern  engineering  and  the  process  of  digging  deep  wells  and  pumping  by  means  of 
engines  might  enable  a  few  families  to  live  comfortably  in  the  Chaco  Canyon,  but  that 
has  nothing  to  do  with  the  matter.  The  former  inhabitants,  no  matter  how  high  may 
have  been  their  civilization,  were  primitive  people  who  had  no  good  tools  and  no  knowledge 
of  mechanics.  They  built  dams  and  ditches  whose  remains  are  found  in  all  parts  of  the 
Southwest,  but  the  abundance  of  these  remains  is  the  best  sort  of  proof  that  the  people 
knew  nothing  of  any  but  the  simple  and  obvious  methods  of  flood  irrigation.  If  they 
had  practised  any  other  sort,  if  they  had  built  dams  of  cut  stone  or  had  constructed  canals 
of  cement,  or  if  they  had  been  able  to  raise  water  out  of  the  depths  of  the  ground,  traces  of 
their  achievements  could  scarcely  fail  to  be  found.  Dry  farming,  it  need  hardly  be  said, 
is  to-day  out  of  the  question  in  this  arid  portion  of  the  country.  How  far  it  was  practised 
in  the  past  is  not  yet  certain,  but  if  our  reasoning  as  to  the  location  of  the  villages  on  the 
plateaus  (and  especially  as  to  the  small,  remote  ruins)  is  correct,  there  probably  was  a  good 
deal  of  it  in  very  ancient  times. 

The  crops  of  the  past  appear  to  have  differed  from  those  of  the  present  not  only  in  quan¬ 
tity  but  in  quality.  I  can  not  vouch  for  the  truth  of  this,  but  Mrs.  Wetherell  and  others 
state  that  the  com  cobs  and  squashes  found  in  the  ruins  are  uniformly  large  like  those  now 
raised  only  in  good  years,  and  not  at  all  like  the  stunted  little  products  of  ordinary  years. 
Whatever  may  have  been  the  quality  of  the  crops  or  the  extent  of  dry  farming,  one  thing 
seems  evident:  Chaco  Canyon  and  the  neighboring  plateaus  to-day,  even  with  modern 
methods  of  irrigation,  could  support  only  a  fraction  of  the  number  of  people  who  appear 
to  have  hved  there  in  the  past.  Either  the  climate  was  different  or  the  ruins  are  utterly 
misleading  in  their  indications  as  to  the  density  of  population. 

7 


82 


THE  CLIMATIC  FACTOK  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Before  leaving  the  Chaco  Canyon  a  word  should  be  added  as  to  the  succession  of 
races  in  this  region.  The  small  villages  or  hamlets  located  upon  the  plateau  at  a  distance 
from  the  main  valleys  seem  to  have  belonged  to  a  people  different  from  those  who  later 
built  the  large  villages,  which,  however,  frequently  contain  evidences  of  an  occupation 
previous  to  that  whose  remains  are  now  chiefly  in  evidence.  For  instance,  at  Pueblo 
Bonita,  Pepper  (who  excavated  for  the  American  Museum  of  Natural  History  in  New 
York)  found  evidences  of  an  older  occupation  10  feet  below  the  one  which  we  have  been 
discussing,  and  there  is  a  possibility  of  an  intermediate  occupation.  Three  feet  under 
the  level  of  the  main  plain  upon  which  stand  the  ruins  of  Pueblo  del  Arroyo  traces  of  old 
walls  can  be  seen  extending  100  feet  beyond  the  present  ruins;  the  lowest  part  of  these 
walls  is  5  feet  below  the  present  surface.  At  the  little  ruin  opposite  Pueblo  Bonita  some 
of  the  walls  extend  downward  3  feet  lower  than  the  others,  suggesting  that  old  walls  had 
fallen  into  ruins  and  were  then  built  upon  once  more  after  3  feet  of  material  had  accumu¬ 
lated.  Elsewhere,  at  points  farther  up  the  canyon,  old  walls  are  said  to  lie  12  feet  below 
the  present  surface.  The  material  in  which  all  these  walls  are  imbedded  seems  to  be  the 
ordinary  silts  of  the  valley  floor.  Without  further  study  no  positive  conclusions  can  be 
based  upon  them,  but  they  are  suggestive.  Apparently  the  Chaco  Valley  was  occupied 
at  least  twice.  Possibly,  although  this  is  pure  surmise,  the  first  occupation  was  at  the 
time  when  the  remoter  ruins  of  the  small  type  were  also  inhabited.  Then  the  place  was 
abandoned,  wholly  or  in  part,  and  the  river  deposited  from  3  to  12  feet  of  silt  before  the 
next  occupation  took  place.  Such  deposition,  as  we  have  seen,  would  normally  occur  in 
a  time  of  unusual  aridity,  and  hence  may  be  of  significance  in  our  climatic  problem. 

The  final  abandonment  of  the  ruins  may  also  throw  light  on  physical  conditions. 
We  have  already  seen  that  at  the  end  of  the  period  of  the  main  occupation  of  the  ruins 
the  inhabitants  were  in  straits  not  only  to  get  water  enough,  as  is  clear  from  their  many 
dams  and  little  reservoirs,  but  also  because  of  enemies,  as  appears  from  the  defensive 
walls  and  from  the  way  in  which  in  neighboring  regions  the  villagers  often  took  refuge  in 
inaccessible  spots  upon  high  hilltops  or  in  deep  canyons.  An  examination  of  the  rooms 
seems  to  indicate  that  the  population  dwindled  gradually.  Many  rooms  are  found  sealed 
up,  or  full  of  rubbish,  showing  that  for  a  long  time  before  their  final  abandonment  they  were 
not  in  use.  All  these  things  are  exactly  what  would  be  expected  if  the  climate  had  become 
drier.  They  can  also,  to  be  sure,  be  explained  equally  well  upon  various  other  suppositions, 
such  as  the  incursion  of  enemies,  or  of  new  people  with  new  ideas,  the  ravages  of  disease, 
the  superstitious  fear  of  rooms  in  which  a  death  has  occurred,  and  other  similar  theories. 
These  might  be  given  the  preference  were  it  not  for  the  evidence  which  we  shall  present 
later  when  we  come  to  discuss  the  measurements  of  trees.  Meanwhile  it  is  merely  necessary 
to  call  attention  to  them. 

One  other  matter  also  comes  up  in  this  connection:  The  region  of  which  the  Chaco 
Canyon  may  be  considered  typical  appears  once  to  have  been  densely  populated,  but  is 
now  one  of  the  least  habitable  places  in  the  United  States.  When  the  Spaniards  arrived  in 
America  the  ancient  inhabitants  appear  already  to  have  vanished,  since  no  mention  is  made 
of  them  in  Spanish  chronicles.  Moreover,  their  pottery  and  methods  of  architecture  were 
different  from  those  of  any  tribe  of  Indians  which  existed  in  later  times.  The  fact  that 
the  people  had  vanished  proves  nothing,  but  it  is  interesting  to  note  that  it  is  exactly  what 
we  should  expect  if  they  were  driven  out  by  aridity.  Here  where  the  country  is  excep¬ 
tionally  dry  they  would  disappear  sooner  than  in  better-watered  regions,  such  as  the  Rio 
Grande  Valley,  where  the  Pueblo  Indians  had  their  chief  center.  We  shall  return  to  this 
general  subject  later  and  its  bearing  will  be  more  fully  apparent. 

One  of  the  best  places  for  the  study  of  the  relation  between  older  and  younger  ruins 
is  the  Pajaritan  Plateau,  20  to  30  miles  northwest  of  Santa  Fe.  I  had  the  good  fortune 
to  be  conducted  to  this  region  by  Mr.  Kenneth  M.  Chapman,  the  assistant  director  of 


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HUNTINGTON 


PLATE  3 


A.  Ruins  of  Tyuonyi  in  the  Canyon  de  los  Frijoles. 

B.  Ruins  of  Pueblo  Bonita  in  Chaco  Canyon. 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


83 


the  Archeological  Museum  of  New  Mexico,  to  whom  reference  has  already  been  made. 
Leaving  the  stiff  shade  trees  of  the  well-watered,  grassy  plaza  of  Santa  Fe,  we  took  the 
narrow-gage  line  of  the  Denver  and  Rio  Grande  Railroad  to  the  lumber  piles  of  the  village¬ 
less  station  of  Buckman  on  the  Rio  Grande  itself.  Crossing  to  the  west  side  of  the  river, 
we  left  the  barren  desert  vegetation  of  yuccas,  sagebrush,  and  cacti  which  prevails  at  this 
altitude  of  5,500  feet,  and  climbed  1,000  feet  to  the  plateau.  The  road  winds  up  over 
variegated  layers  of  volcanic  tuff  of  pale^  pink,  yellow  or  brilliant  orange  shades,  inter¬ 
spersed  with  the  darker  blue-black  of  basaltic  lava  flows  and  capped  with  brick-red  columnar 
tuffs.  These  volcanic  rocks  form  the  Pajaritan  Plateau,  a  gently  sloping,  deep-soiled 
district,  sharply  cut  by  numerous  canyons  formed  by  streams  running  eastward  from  the 
Jemez  Mountains.  The  plateau  is  a  beautiful  region  covered  with  forests  of  juniper  and 
pinon,  which  at  higher  elevations  give  place  to  stately  yellow  pines  set  in  open  order  with 
stretches  of  sparse  grass  between  them.  The  scenery  is  uncommonly  attractive  as  one 
drives  slowly  along,  sometimes  on  the  level,  again  dropping  into  the  hollow  at  the  head  of  a 
canon,  and  then  climbing  the  slope  once  more  to  the  upland,  where  one  looks  out  east  or 
west  at  great  snowy  mountains.  Yet  in  spite  of  the  deep  soil,  the  grass,  and  the  trees, 
we  saw  no  sign  of  modern  habitation,  for  except  in  a  few  insigniflcant  spots  in  the  bottoms 
of  the  canons  where  irrigation  is  possible,  all  the  great  plateau  is  too  dry  for  cultivation 
below  a  level  of  about  8,000  feet. 

Soon  after  we  had  reached  the  main  top  of  the  plateau  we  came  upon  the  flrst  of  the 
great  number  of  ruins  which  are  scattered  in  all  parts.  These  particular  ones  were  cliff 
dwelhngs  of  the  usual  type,  caves  dug  in  the  soft  volcanic  rock  on  the  side  of  a  shallow 
canyon,  and  fronted  by  rooms  made  of  blocks  of  the  same  soft  tufa.  The  number  of 
such  caves  and  cliff  dwelhngs  in  this  one  Pajaritan  Plateau  is  literally  thousands.  With 
them  are  associated  other  villages  of  the  same  type  as  those  of  the  Chaco  Canyon.  After 
crossing  several  minor  canyons  we  reached  the  edge  of  the  deep  Canyon  of  El  Rito  de  Los 
Frijoles,  or  Bean  Canyon,  where  a  precipitious  cliff  falls  away  400  feet  or  more  at  one’s 
feet.  Looking  over  the  brink  of  the  cliff  one  sees,  far  down  at  the  base  of  a  precipice,  a 
structure  which  at  flrst  sight  suggests  a  Greek  amphitheater;  it  is  the  village  of  Tyuonyi, 
excavated  by  the  School  of  American  Archeology  at  Santa  Fe  in  the  four  seasons  from 
1908  to  1911.  The  plan  of  the  ruins  is  symmetrical,  a  circle  shghtly  flattened  on  the 
north  side,  and  containing  five  to  eight  tiers  of  rooms  arranged  hke  the  seats  of  a  theater. 
Across  the  flattened  end  where  the  stage  would  be  expected,  a  line  of  rooms  contains  the 
remnants  of  three  circular  chambers  or  “kivas,”  designed  for  religious  purposes,  and 
apparently  analogous  to  the  larger  circular  or  elliptical  structures  which  are  found  so 
commonly  among  the  ruins  of  adobe  and  wattle  villages  in  the  Santa  Cruz  Valley  and 
other  regions  farther  south.  (See  Plate  3,  a). 

The  Canyon  of  El  Rito  de  Los  Frijoles  contains  not  only  the  main  ruins  of  Tyuonyi  and 
several  smaller  ones,  but  also  a  great  number  of  caves  and  cliff-dwellings.  Doubtless  the 
caves  were  at  first  the  chief  homes  of  the  aborigines;  but  as  time  went  on  and  a  higher  stage 
of  civihzation  was  reached,  they  were  used  chiefly  as  store  rooms,  and  the  main  life  of 
the  households  was  conducted  in  rooms  located  in  front  of  the  caves  and  built  of  stone 
plastered  with  mud.  Often  a  house  consisted  of  three  tiers  of  rooms  in  front  of  a  cave; 
and  in  many  cases  the  rooms  were  built  one  on  top  of  another  to  a  height  of  three  stories. 
Most  of  the  rooms,  like  those  of  all  the  primitive  people  of  the  Southwest  as  well  as  the 
modern  Pueblos,  were  entered  through  the  roof.  The  small  size  of  the  rooms,  not  over 
6  feet  by  10  on  an  average,  is  surprising.  The  reason  commonly  assigned,  however,  seems 
convincing.  On  the  high  Pajaritan  Plateau  the  temperature  often  falls  to  10°  F.  below 
zero.  The  relatively  dense  population  must  quickly  have  used  up  all  the  available  dead 
firewood  for  many  miles  around,  and  it  was  no  easy  task  for  a  primitive  people,  unsupplied 
with  iron  tools,  cut  to  firewood  sufficient  for  anything  more  than  the  necessities  of  cooking. 


84 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Farther  south,  or  at  lower  altitudes,  the  rooms  were  larger,  for  there  it  was  easy  to  keep 
warm. 

The  low  temperature  of  the  Pajaritan  Plateau  does  not  appear  to  have  diminished  the 
number  of  inhabitants.  Frijoles  Canyon  alone,  within  a  distance  of  not  over  1.5  miles 
up  and  down  the  narrow  gorge,  had  a  population  of  fully  2,000  souls  according  to  the 
estimate  of  Dr.  Edgar  L.  Hewett,  Director  of  the  School  of  American  Archeology,  who 
was  personally  in  charge  of  the  excavations.  The  actual  number  of  rooms,  including  the 
village  ampliitheater,  the  caves,  and  the  chff  dwellings,  appears  to  have  amounted  to 
about  3,000.  At  present,  according  to  Judge  Abbott,  who  owns  all  the  valley  except  the 
ruins,  the  amount  of  land  that  can  be  irrigated  amounts  to  21  acres.  The  ancient  Pajaritans 
could  scarcely  have  existed  unless  they  cultivated  the  plateau  where  now  not  a  solitary 
person  makes  a  living  from  the  fruits  of  the  earth.  Therefore  Dr.  Hewett  is  unqualifiedly 
of  the  opinion  that  the  climate  of  the  past  was  moister  than  that  of  the  present. 

Let  us  now  consider  an  apparently  older  and  more  widely  scattered  occupation  of  the 
country.  During  our  visit  to  the  plateau  we  watched  carefully  not  only  for  cave  dwellings 
and  villages  of  the  Tyuonyi  type,  but  for  the  little  mounds  which  here  and  there,  at  a  distance 
from  all  the  main  sources  of  water  both  past  and  present,  proclaim  the  location  of  houses 
scattered  over  the  plateau.  One  not  closely  on  the  watch  may  miss  these  entirely,  for 
they  are  merely  small  heaps  of  stones.  In  the  space  of  7  miles  we  saw  houses  of  this  type 
within  sight  of  the  road  in  49  different  places.  Inasmuch  as  several  houses  were  often 
clustered  in  one  group,  the  total  number  of  dwellings  was  67.  They  were  obviously  mere 
farm-houses,  but  some  had  from  8  to  20  rooms,  and  must  have  been  inhabited  by  more 
than  one  family.  Therefore  in  our  7-mile  ride  through  the  open,  park-like  forest  we  must 
have  found  the  dwellings  of  approximately  100  families  within  sight  of  the  road.  It  would 
be  a  populous  farming  district  in  any  part  of  England  where  one  could  find  100  famihes  on 
7  miles  of  road.  We  can  not,  of  course,  assume  that  every  one  of  these  houses  was  occupied 
at  one  time,  but  it  is  not  probable  that  any  large  number  were  vacant  at  a  time  when  new 
ones  were  being  built.  The  blocks  of  stone  used  in  their  construction  would  seem  to  be 
too  valuable  to  permit  of  their  being  wasted  when  new  houses  were  to  be  erected.  Even 
in  these  days  of  metal  tools,  beasts  of  burden,  and  wheeled  carts  many  great  ruins  of  western 
Asia  are  in  imminent  danger  of  being  utterly  destroyed  by  the  natives,  who  carry  away  the 
stone  for  use  in  new  houses,  even  though  the  present  population  is  only  a  fraction  of  that 
of  the  past.  In  the  days  of  the  Pajaritans,  when  the  blocks  of  stone  had  to  be  hewn  w'ith 
stone  axes  and  carried  from  the  quarries  in  the  canyons  on  the  backs  of  men  or  rather  of 
women,  we  can  scarcely  believe  that  the  people  were  so  extraordinarily  industrious,  or  so 
superstitious,  that  for  generation  after  generation  they  would  leave  good  stones  in  ruins 
close  at  hand  and  go  to  the  labor  of  obtaining  new  ones.  Therefore  we  are  inclined  to 
believe  that  at  the  height  of  the  prosperity  of  this  region  practically  every  one  of  the 
present  ruins  was  a  house  occupied  by  one  or  more  families. 

These  scattered  little  ruins  of  farm-houses,  almost  unnoticed  even  by  the  archeologist, 
present  one  of  the  most  interesting  problems  in  American  archeology.  The  potsherds 
found  in  them  are  different  from  those  in  the  larger  villages  or  in  the  majority  of  the  cliff- 
dwellings  immediately  around  them.  The  pottery  of  the  farms,  as  Mr.  Chapman  points 
out,  is  almost  wholly  a  fine-grained  ware  painted  white  and  adorned  with  geometrical 
designs  in  black.  In  the  larger,  more  modern  ruins,  however,  only  a  httle  of  this  is  found, 
while  the  commonest  kinds  are  a  coarser  white  ware  with  more  abundant  curves  in  the 
designs,  and  a  wholly  different  type  of  red  ware  adorned  with  black  figures  decorated  with  a 
species  of  glaze.  These  differences,  coupled  with  other  evidence,  such  as  the  manifestly 
greater  age  of  the  small  isolated  ruins,  show  that  here,  even  more  plainly  than  in  the 
Chaco  region,  we  have  to  do  with  two  occupations  as  distinct  from  one  another  (and  from 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


85 


the  later  and  far  less  extensive  Pueblo  occupation)  as  is  the  modern  American  occupation 
from  that  of  the  Spaniards.  The  first  inhabitants  spread  far  more  widely  than  their 
successors.  They  seem  to  have  felt  no  need  of  being  near  the  main  sources  of  water  nor 
yet  of  gathering  together,  as  the  later  people  did,  in  places  which  could  easily  be  defended. 
For  a  long  period  before  the  advent  of  the  enemy  which  finally  displaced  them,  their  lives 
were  apparently  free  and  comfortable  in  their  high  forest  homes.  How  or  why  they 
vanished  is  as  unknown  to  us  as  is  their  origin,  but  perchance  we  shall  learn  the  story 
little  by  httle.  It  will  not  be  a  story  of  peace  and  monotony,  for  those  are  not  the  conditions 
which  prevail  when  a  race  comes  into  a  country  nor  when  it  is  forced  out.  We  can  scarcely 
doubt  that  raids,  plunder,  repeated  invasions,  great  distress,  and  the  final  disappearance 
of  one  type  of  civilization  and  its  replacement  by  another  were  the  order  of  events. 

This  painful  process  of  a  change  of  civilization  took  place  not  once  alone,  but  at  least 
twice.  Formerly  the  cliff-dwellers  who  built  the  compact  villages  like  Tyuonyi  and  Pueblo 
Alto  were  supposed  to  have  been  of  the  same  race  as  the  modern  Pueblo  Indians,  but 
recent  investigations  indicate  that  this  is  not  true.  Possibly,  indeed  probably,  the  modern 
Pueblo  is  related  to  the  second  or  village-building  type  of  ancient  inhabitants,  whom  we 
may  call  Pajaritans  in  distinction  from  the  still  older  type  who  may  perhaps  be  classed  as 
Hohokam,  but  the  relationship  is  not  close.  The  bones  of  the  dead,  exhumed  after  cen¬ 
turies,  tell  something  of  the  tale.  The  modern  Pueblo  Indians  are  brachycephalic  accord¬ 
ing  to  Dr.  Hrdlicka;*  their  heads  are  relatively  broad,  as  anyone  can  tell  by  looking  at  them. 
Some,  however,  are  dolichocephalic,  with  long  heads,  but  these  are  in  a  minority.  The 
present  Indians  are  clearly  of  mixed  descent.  Their  predecessors,  on  the  contrary,  were  of 
a  pure  race,  predominantly  long-headed  like  ourselves.  Therefore  we  infer  that  they  were 
conquered  by  invading  broad-heads,  and  that  finally  the  invading  broad-heads  and  as 
many  of  the  long-heads  as  had  neither  fled  nor  perished  became  amalgamated  into  a 
single  race.  Perhaps  the  ancient  farmers,  the  medieval  villagers,  and  the  modern  Pueblo 
Indians  were  not  the  only  races  which  have  passed  across  the  stage  of  history  in  the  pre¬ 
historic  days  of  America.  In  other  parts  of  the  Southwest  faint  glimmerings  of  still 
other  cultures  are  seen,  which  show  that  change  and  movement  have  been  as  characteristic 
of  the  ancient  history  of  America  as  of  that  of  Europe  and  Asia. 

We  have  seen  that  at  least  two  types  of  prehistoric  civilization  spread  widely  over 
areas  which  are  now  uninhabitable.  The  early  Hohokam  farmers  have  left  their  ruins 
over  all  parts  of  the  high  plateaus  and  of  the  great  lowland  valleys  far  from  any  visible 
source  of  water,  even  for  drinking.  The  later  Pajaritans,  both  village-  and  cliff-dwellers, 
did  not  spread  so  widely,  but  they  managed  to  live  and  raise  food  in  hundreds  of  valleys 
where  this  now  seems  to  be  impossible.  Let  us  next  inquire  whether  the  latest  of  the 
original  American  types  of  civilization,  the  Pueblo  Indians,  were  ever  blessed  with  climatic 
conditions  such  that  they,  too,  could  inhabit  regions  whence  drought  now  excludes  them. 

The  well-known  ruins  of  Tabira,  popularly  called  Gran  Quivira,  are  located  about  6,000 
feet  above  the  sea  near  the  center  of  New  Mexico,  about  65  miles  south-southeast  of  Albu¬ 
querque.  They  lie  on  a  rounded  hill,  about  200  feet  above  a  broad,  open  valley  draining 
toward  the  south  and  a  mile  or  more  in  width.  The  ruins  consist  of  two  distinct  portions, 
Pueblo  and  Spanish.  The  ground  area  is  about  700  by  350  feet,  with  a  few  buildings  out¬ 
side  these  limits.  All  the  structures  were  built  of  light-gray  limestone  broken  into  roughly 
rectangular  blocks.  The  exact  source  of  the  building  material  is  not  evident,  although  there 
is  stone  of  the  same  sort  visible  in  small  outcrops  not  far  away.  The  character  of  the  stone, 
however,  is  such  that  it  would  be  difficult  to  get  it  out  in  large  quantities  without  the 
aid  of  explosives.  Inasmuch  as  the  village  was  evidently  built  long  before  the  coming  of 
the  Spaniards,  we  must  assume  that  the  Indians  put  themselves  to  a  vast  amount  of  labor 
in  the  process  of  quarrying,  squaring,  and  transporting  the  stones  of  their  numerous  houses. 


*See  Hewett,  Edgar  L.:  The  Pajaritan  Culture.  Papers  of  the  School  of  American  Archaeology,  No.  3,  p.  341. 


86 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Many  of  the  dwellings  appear  to  have  been  of  two  stories,  and  the  height  of  the  heaps  of 
rocks  makes  it  probable  that  some  had  at  least  three  stories.  The  rooms  are  all  small  as 
is  usual  in  this  region,  the  majority  not  exceeding  7  by  9  feet.  The  exact  number  of  rooms 
has  never  been  counted,  but  some  approximate  idea  may  be  obtained.  If  we  assume  that 
only  half  of  the  5.5  acres  covered  by  the  ruins  was  actually  built  upon  and  that  the  rooms 
including  the  walls  had  an  average  size  of  10  feet  by  10,  there  would  have  been  about  1,100 
rooms  on  the  ground  floor.  The  upper  stories  may  be  put  at  400  rooms,  although  the  actual 
number  was  probably  greater.  This  gives  1,500  rooms  as  a  moderate  estimate,  which  would 
mean  at  least  1,000  people. 

When  the  Spaniards  came  to  the  country,  at  the  beginning  of  the  seventeenth  century, 
the  village  of  Gran  Quivira  was  evidently  one  of  the  most  important  in  the  district.  Other¬ 
wise  the  canny  fathers  would  not  have  built  here  one  of  their  largest  missions.  Building 
stone  was  fairly  easy  to  obtain,  it  would  seem,  inasmuch  as  the  walls  of  the  church  are  5 
feet  thick.  Possibly  this  was  because  a  portion  of  the  village  was  in  ruins,  and  the  stones 
from  it  were  available  as  building  materials  for  the  large  church  and  other  structures  which 
the  Spaniards  erected.  Nevertheless,  the  number  of  natives  must  have  been  considerable, 
or  there  would  have  been  no  reason  for  a  mission.  The  beginning  of  the  Spanish  regime 
here,  as  in  the  rest  of  New  Mexico,  appears  to  have  been  peaceful  and  prosperous.  Its 
end,  so  far  as  Gran  Quivira  is  concerned,  seems  to  have  come  shortly  before  the  Pueblo 
rebellion,  which  culminated  in  1680.  Since  that  time  the  site  has  been  left  as  a  center 
around  which  a  multitude  of  traditions  has  gathered.  One  ascribes  its  destruction  to  an 
earthquake,  another  to  a  flow  of  lava  bursting  forth  some  miles  away,  and  still  a  third 
speaks  of  a  river  which  has  now  disappeared. 

The  truth  seems  to  be  that  there  is  no  village  now  at  Gran  Quivira  because  there  is  no 
water  and  the  land  is  too  dry  for  successful  cultivation  except  in  years  of  good  rainfall. 
A  ranch  is  located  in  the  valley  below  the  ruins,  but  it  is  not  permanently  inhabited, 
although  a  little  cultivation  is  carried  on.  Settlers  have  recently  come  into  the  region  10 
to  15  miles  to  the  north,  but  are  having  a  hard  time.  If  the  rainfall  is  propitious  they 
can  exist,  but  in  1909  none  of  them  raised  enough  to  live  on.  It  scarcely  need  be  added 
that  all  depend  upon  deep  wells  for  water.  The  Pueblo  Indians,  so  far  as  we  can  gather, 
were  like  their  Hohokam  predecessors  in  knowing  nothing  of  lime  or  mortar  and  had  no 
facilities  for  making  water-tight  cisterns.  Often,  however,  they  constructed  reservoirs, 
which  were  their  main  dependence.  One  such  reservoir  still  remains  intact  at  Gran 
Quivira.  It  lies  about  0,25  mile  east  of  the  village  in  the  mouth  of  a  shallow  arroyo,  as 
dry  valleys  are  here  called.  The  reservoir  is  only  about  75  feet  in  width  and  5  feet  deep. 
The  owners  of  the  ranch  down  below  in  the  main  valley  say  that  during  7  years  of  life  here 
they  have  never  seen  any  water  in  it  except  immediately  after  rain.  My  visit  took  place 
in  the  early  spring  of  1911,  after  a  more  than  commonly  rainy  season.  The  day  previous 
to  that  on  which  I  started  from  the  railroad  at  Willard,  30  miles  to  the  north,  there  was  a 
heavy  storm,  and  during  the  drive  we  were  soaked  in  a  pouring  rain.  Nevertheless,  the  next 
morning  the  reservoir  contained  no  water  and  showed  no  sign  of  having  held  more  than  a 
small  pool  the  day  before.  In  all  the  region  within  a  score  of  miles  of  Gran  Quivira  there  is 
only  one  permanent  spring.  That  is  located  7  miles  to  the  west  at  Montezuma,  and,  as 
might  be  expected,  has  its  own  ruins  of  an  ancient  village.  Strangely  enough,  however,  the 
Montezuma  village  was  evidently  abandoned  long  before  Gran  Quivira.  This  suggests 
that  the  difficulty  of  raising  crops  was  a  more  serious  matter  than  the  difficulty  of  obtaining 
water.  At  Montezuma  the  land  does  not  lie  so  low  and  flat  as  at  Gran  Quivira  and  is  not 
flooded,  as  are  the  lowlands  of  the  latter  place,  during  summers  when  the  rainfall  is  large. 

In  addition  to  Gran  Quivira  another  similar  ruin  of  a  Spanish  mission  deserves  to  be 
recalled  in  order  to  show  that  the  phenomena  just  described  are  not  isolated.  This  is  the 
ruin  of  Buzani,  which  has  already  been  mentioned  as  lying  about  12  miles  below  Caborca 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


87 


on  the  lower  Altar  River  in  northwestern  Mexico.  Caborca,  it  will  be  remembered,  is  the 
last  inhabited  place  on  the  river.  Farther  downstream  there  is  no  water  except  during  the 
brief  season  of  floods.  At  Buzani  a  few  Papago  Indians  cultivate  a  considerable  quantity 
of  land  in  good  years,  but  do  not  live  there  all  the  time.  They  might  remain  through  the 
year,  for  they  have  a  well,  but  it  is  very  deep,  and  the  labor  of  drawing  water  is  great. 
Here,  as  in  the  other  case,  the  Spaniards  established  a  mission  in  a  place  which  sensible 
people  would  now  scarcely  choose  for  the  purpose.  I  have  not  been  able  to  ascertain  the 
date  of  the  Buzani  church,  and  am  not  certain  whether  it  dates  from  the  seventeenth  or 
eighteenth  century,  but  probably  from  the  latter.  Its  evidence  is  by  no  means  so  clear  or 
pronounced  as  that  of  the  Gran  Quivira.  In  both  cases,  however,  the  point  to  be  borne  in 
mind  is  this:  we  have  before  us  two  theories  which  stand  on  an  absolutely  equal  footing 
so  far  as  innate  probability  is  concerned.  The  only  question  is  which  one  best  fits  all  the 
facts.  One  theory  holds  that  the  climate  of  the  past  tliree  centuries  has  been  uniform; 
while  the  other  assumes  that  there  has  been  a  change,  the  seventeenth  century  or  at  least 
its  first  half  presumably  having  been  considerably  moister  than  the  nineteenth,  while  the 
eighteenth  was  probably  intermediate  between  the  other  two.  Viewing  the  two  theories 
without  prejudice,  it  seems  fair  to  say  that  the  theory  of  change  fits  the  facts  better  than 
the  theory  of  uniformity. 

We  have  now  finished  our  survey  of  the  ruins  of  the  United  States.  Let  us  sum  up  our 
conclusions,  and  see  whither  they  have  led  us  and  what  possibilities  they  suggest.  The 
evidence  that  the  climate  of  the  past  was  different  from  that  of  the  present  seems  to  be  too 
strong  to  be  ignored.  The  simplest  mathematical  calculation  shows  that  where  it  is  possible 
to  raise  food  for  only  10  people  100  people  never  could  have  found  sustenance.  Neverthe¬ 
less,  many  men  whose  opinion  is  entitled  to  the  greatest  respect  doubt  the  conclusion  to 
which  this  simple  sum  in  division  would  seem  to  lead.  They  admit  that  100  people  could 
never  have  lived  in  the  places  which  furnish  food  for  only  10,  but  say  that  the  solution 
of  the  problem  is  not  to  multiply  the  ancient  food  supply  by  10,  but  to  divide  the  apparent 
population  by  10.  Their  argument  does  not  seem  to  be  conclusive,  because  it  involves  the 
assumption  that  the  people  of  the  past  were  radically  different  from  those  of  the  present; 
yet  such  arguments  are  extremely  difficult  to  discuss,  because  no  one  can  assert  that 
certain  races  of  people  may  not  have  had  habits  quite  contrary  to  those  of  the  rest  of  the 
world.  The  burden  of  proof,  assuredly,  is  on  those  who  assume  such  peculiarities  in  the 
ancient  Americans,  and  it  seems  as  if  they  had  not  proved  their  point,  but  this  is  purely  a 
matter  of  opinion.  If  there  were  no  other  way  of  settling  the  question  it  would  be  necessary 
to  take  up  this  matter  step  by  step  and  discuss  the  exact  degree  of  mobility  among  modern 
races  of  various  degrees  of  development,  and  then  to  go  on  to  an  attempt  at  estimating 
the  exact  amount  of  food  that  could  be  supplied  in  the  best  as  compared  with  the  worst 
years.  Then  we  should  have  to  calculate  the  number  of  people  who  could  possibly  have 
made  a  living  and  to  compare  that  with  the  number  whom  the  ruins  seem  to  indicate. 
Next  we  should  have  to  estimate  the  amount  of  work  which  would  be  required  to  build 
such  ruins  as  those  of  Pueblo  Bonita,  for  example,  and  should  have  to  determine  how  many 
decades  or  centuries  of  constant  labor  the  construction  of  all  the  numerous  ruins  in  and 
around  the  Chaco  Canyon  would  have  required  on  the  part  of  the  handful  of  people  who 
could  there  find  sustenance.  When  that  was  finished,  we  might  perhaps  be  in  a  position 
to  say  just  how  phenomenal  must  have  been  the  ancient  race  which  migrated  so  quickly 
from  place  to  place,  and  worked  so  hard  in  order  to  leave  ruins  that  look  as  if  they  had 
been  the  work  of  many  people  instead  of  a  few.  By  the  time  we  had  finished  we  should 
have  made  so  many  assumptions  that  our  conclusions  would  be  inconclusive,  and  we 
should  end  where  we  began. 

The  only  way  to  arrive  at  a  firm  conclusion  is  to  test  the  matter  by  some  means  which 
does  not  involve  any  assumptions  as  to  the  nature  of  man,  either  now  or  in  the  past.  Such 


88 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


means  are  found  in  the  old  strands  and  terraces  described  in  earlier  chapters.  Even  these, 
however,  are  not  conclusive  in  certain  respects.  As  to  the  alluvial  terraces  there  is  an 
alternative  theory,  that  of  earth  movements,  which  has  hitherto  been  so  widely  accepted 
that  the  student  who  has  a  bias  against  changes  of  chmate  is  almost  sure  to  inchne  toward 
it.  As  to  the  lakes,  there  can  be  little  question  that  their  high  strands  indicate  moist 
conditions  in  relatively  recent  times,  but  when  it  comes  to  dating  those  times,  we  are 
once  more  at  a  loss  to  determine  convincingly  whether  they  belong  to  a  period  before  or 
after  the  coming  of  the  Hohokam.  Taking  it  all  in  all,  then,  we  may  say  that  if  we  accept 
the  reasoning  of  this  volume  as  to  the  origin  of  alluvial  terraces,  and  if  we  assume  that  the 
Hohokam  were  essentially  like  the  rest  of  mankind,  the  evidence  in  favor  of  changes  of 
climate  is  overwhelming.  If,  on  the  contrary,  we  accept  the  tectonic  theory  of  the  origin 
of  terraces,  and  assume  that  the  Hohokam  were  a  highly  pecuhar  people,  we  nulhfy  the 
strongest  arguments  in  favor  of  climatic  changes,  but  we  do  not  thereby  prove  that  climatic 
uniformity  has  been  the  rule.  We  merely  leave  the  matter  open.  The  theory  of  uni¬ 
formity  needs  exactly  as  much  proof  as  that  of  change,  for  the  inherent  probability  of 
the  one  is  the  same  as  that  of  the  other.  Yet,  so  far  as  I  am  aware,  no  one  has  ever  ade¬ 
quately  supported  the  theory  of  uniformity  by  means  of  an  array  of  well-digested  facts  and 
figures,  although  many  people  have  sought  to  disprove  the  arguments  advanced  as  indica¬ 
tive  of  changes.  The  matter  can  not  be  finally  settled  until  actual  measurements  of 
specific  phenomena  at  specific  dates  can  be  obtained.  Such  measurements  wiU  be  pre¬ 
sented  in  later  chapters.  Meanwhile,  the  evidence  already  set  forth  is  in  itself  so  indicative 
of  changes  of  climate,  and  agrees  so  closely  with  all  that  has  been  observed  in  Asia,  that 
we  seem  forced  at  least  to  believe  that  a  change  of  climate  in  the  southwestern  part  of  the 
United  States  is  quite  as  probable  as  no  change. 

As  to  whether  the  supposed  change  from  the  past  to  the  present  was  pulsatory  or 
gradual  the  evidence  is  not  so  strong.  The  terraces,  and  to  a  less  extent  the  lacustrine 
strands  and  gypsum  dunes,  seem  to  point  to  a  pulsatory  character.  The  human  evidence 
is  less  conclusive.  Since  the  pre-Columbian  inhabitants  of  America  began  their  work, 
however,  the  course  of  history  appears  to  have  been  characterized  by  three  chief  epochs.  In 
the  first  epoch  man  spread  over  wide  areas,  lived  peacefully  in  small,  unsheltered  commu¬ 
nities,  and  apparently  was  not  particularly  disturbed  as  to  his  supply  of  water.  Then  this 
population  of  early  farmers  disappeared.  How  or  why  or  when,  we  can  not  tell.  War, 
pestilence,  drought,  or  any  one  of  a  dozen  different  disasters  may  have  been  the  cause. 
Some  of  the  people  may  have  gone  at  one  time,  and  others  centuries  later.  All  that  we 
know  is  that  they  went  and  were  succeeded  by  a  people  who  lived  a  different  sort  of  life. 
At  first  these  later  people  may  have  been  as  peaceful  and  untroubled  as  their  predecessors, 
but  before  they  finally  left  their  ruins  they  were  forced  to  cluster  around  the  main  supplies 
of  water,  they  were  compelled  to  build  dams  and  reservoirs  in  large  numbers,  and  they 
were  sadly  harassed  by  relentless  enemies.  In  their  case,  also,  we  have  no  exact  knowledge 
as  to  whether  war,  pestilence,  drought,  or  other  causes  finally  overwhelmed  them,  but 
this  much  can  fairly  be  said :  All  the  disasters  which  have  been  suggested  as  the  chief  cause 
of  their  decline  are  the  sort  wliich  would  arise  when  the  climate  became  dry,  the  crops 
failed,  famine  was  rife,  disease  had  free  rein  because  of  the  weakening  due  to  poor  nourish¬ 
ment,  and  war  and  plunder  were  rampant  because  of  discontent  and  suffering.  How  many 
of  this  second  type  of  people  were  displaced  at  any  one  time,  how  long  they  suffered  before 
they  were  driven  out,  and  how  long  they  had  previously  dwelt  in  safety  no  one  yet  knows. 
Probably  they  had  disappeared,  or  their  villages  had  been  abandoned  and  they  had  become 
mixed  with  the  invading  Pueblos  at  least  two  or  three  centuries  before  the  Spaniards 
arrived  about  1600  a.  d.,  for  otherwise  the  early  fathers  would  have  heard  traditions  of 
them  in  greater  numbers.  More  than  that  we  can  not  say.  Finally,  the  last  type  of 
aborigines,  the  Pueblo  Indians,  have  had  a  history  similar  to  that  of  their  predecessors,  but 


SUCCESSIVE  STAGES  OF  CULTUEE  IN  NORTHERN  NEW  MEXICO. 


89 


on  a  much  less  extensive  scale.  They,  too,  in  the  early  part  of  the  seventeenth  century 
seem  to  have  been  able  to  spread  out  into  regions  not  now  habitable,  and  they,  too,  suffered 
stress  and  were  forced  to  give  up  their  old  homes. 

The  history  thus  outlined  is  highly  fragmentary.  It  is  introduced  here  merely  to  call 
attention  to  the  way  in  which  studies  like  those  of  this  volume  may  enable  us  to  round  out 
the  outlines  of  early  American  history  and  assign  dates  to  certain  epochs.  If  the  change 
of  climate  from  the  past  to  the  present  has  been  pulsatory,  it  needs  no  demonstration  to 
show  that  in  a  dry  country  like  the  Southwest  an  epoch  of  abundant  and,  still  more,  of 
increasing  rainfall  would  be  marked  by  prosperity  and  by  an  increase  in  the  density  of 
population.  Wars  would  be  relatively  scarce,  or  if  they  occurred  they  would  be  wars  of 
conquest  and  expansion  rather  than  pitiless  raids  like  those  of  the  hungry  Arabs  and  the 
hordes  of  Genghis  Khan.  Such  at  least  is  the  theory  to  which  a  study  of  the  climatic 
vicissitudes  of  Asia  seems  to  lead.  When  a  change  for  the  worse  arose,  and  the  country 
began  to  become  drier,  all  sorts  of  distress  would  ultimately  ensue.  That  drought  brings 
famine,  and  that  famine  brings  disease  and  pestilence,  need  no  demonstration.  That 
famine  and  hardship  lead  to  robbery,  raids,  plunder,  and  kindred  ills  is  also  self-evident. 
That  these  things  disrupt  society  and  lead  to  war,  misery,  and  the  overthrow  of  civilizations 
is  also  clear.  Doubtless  other  forces  often  conceal  and  often  reverse  the  results  which 
climate  alone  would  produce,  but  even  in  the  most  advanced  of  modern  countries  few 
influences  are  more  powerful  than  those  of  poor  crops,  poverty,  and  hunger.  For  example, 
Bruckner*  has  shown  that  the  volume  of  emigration  from  northwestern  Europe  to  the 
United  States  has  varied  in  close  harmony  with  variations  in  rainfall  and  hence  in  the 
crops.  Moist  periods  in  Europe  are  in  general  coincident  with  moist  periods  in  America, 
but  in  northwestern  Europe  an  excess  of  moisture  is  injurious  to  most  farm  products,  while 
in  America  it  is  favorable.  Hence  poverty  at  home  has  served  as  an  expulsive  force,  while 
prosperity  in  America  has  been  an  attractive  force,  and  the  two  together  have  caused  a 
pronounced  agreement  between  rainfall  and  emigration,  as  is  illustrated  in  figure  7.  To 


Fig.  7. — Rainfall  and  Emigration  in  Europe,  after  Briickner. 

take  another  example,  it  is  generally  agreed  that  the  United  States  had  a  Populist  party 
largely  because  of  a  series  of  bad  crops,  and  that  the  party  died  on  the  return  of  prosperity. 
If  small  variations  of  rainfall  can  produce  such  great  results,  a  far  more  serious  and  pro¬ 
longed  succession  of  worse  and  worse  years  might  well  disrupt  so  primitive  a  civilization 
as  that  of  the  pre-Columbian  Americans.  If  this  is  so,  and  if  we  shall  ultimately  find  that 
chmatic  pulsations  have  actually  taken  place,  we  shall  be  able  to  say  that  in  such  and 
such  centuries  the  conditions  of  climate  were  such  that  prosperity  was  the  rule,  and  that 
agriculture  was  possible  to  such  and  such  limits.  In  certain  succeeding  centuries,  when 
conditions  became  worse,  the  inhabitants  must  have  been  forced  to  find  a  living  within 
an  area  much  smaller  than  heretofore,  old  habits  must  have  been  interfered  with,  war 
and  strife  must  have  prevailed,  numbers  of  people  must  have  been  forced  to  move  from 

*  Ed.  Bruckner:  Edimaschwan  kungen  und  Volker  wanderungen  in  xix  Jahrhundert  Internationaler  Wochenschrift. 
Marz  5, '.1910. 


90 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


one  place  to  another,  and  in  general  the  conditions  of  life  must  have  been  revolutionized. 
In  this  way  it  is  quite  possible  that  we  may  be  able  to  date  and  characterize  some  of  the 
chief  epochs  in  early  American  history. 

As  has  already  been  stated,  the  more  severe  climatic  variations  of  the  present  time 
appear  to  be  in  general  synchronous  in  the  United  States  and  Europe.  This  was  evident 
in  the  summer  of  1911,  when  England  was  so  dry  as  to  be  changed  from  a  green  land  to  a 
brown,  and  the  eastern  United  States  had  the  hottest,  driest  season  for  a  century.  If 
larger  climatic  variations  are  likewise  synchronous  in  both  hemispheres  the  chronology  of 
climatic  changes  which  has  been  worked  out  in  Asia  may  assist  in  the  elucidation  of  the 
unwritten  history  of  America.  In  Asia  each  of  several  great  dry  epochs  seems  to  have  been 
marked  by  great  movements  of  the  nations  and  by  the  more  or  less  complete  reorganization 
of  society  in  the  regions  which  were  most  influenced.  The  first  such  epoch  can  be  dimly 
discerned  about  1200  b.  c.  At  that  time  the  ancestors  of  the  Greeks  came  into  their 
peninsula,  the  Hebrews  entered  Palestine,  the  Aramaeans  from  Arabia  spread  out  into 
Babylonia  and  all  the  neighboring  lands,  and  Egypt  was  overwhelmed  by  invaders  from 
both  the  Libyan  and  Arabian  deserts.  The  next  great  period  of  aridity  apparently  culmi¬ 
nated  in  the  seventh  century  after  Christ  or  thereabouts.  Its  approach  seems  to  have 
been  marked  by  the  barbarian  invasions  of  Europe  and  its  culmination  by  the  Mohammedan 
outpouring  from  Arabia.  Finally,  the  third  of  the  more  important  dry  epochs  came  about 
1200  A.  D.,  when  the  hordes  of  Genghis  Khan  ravaged  Asia  from  China  to  the  Mediter¬ 
ranean.  Besides  these  more  intense  periods  of  aridity  there  seem  to  have  been  others  of 
minor  importance,  but  these  may  here  be  omitted.  Between  the  epochs  of  aridity  periods 
of  prosperity,  expansion,  and  growth  have  apparently  coincided  with  favorable  conditions 
of  climate.  In  studying  the  ruins  of  America  we  have  thus  far  found  no  data  which  enable 
us  to  correlate  the  climatic  history  of  the  Old  World  and  the  New.  Nevertheless,  we  find 
in  each  continent  three  main  periods  of  prosperity  and  apparently  of  abundant  precipi¬ 
tation  in  the  drier  portions.  Perhaps  this  may  be  due  to  an  actual  agreement  in  climatic 
events.  The  ancient  and  widely  extended  farming  population  of  the  remote  little  ruins 
of  our  southwestern  plateaus  may  have  lived  in  the  period  of  moist  chmatic  conditions  of 
which  we  seem  to  find  evidence  at  the  time  of  Christ  and  earher.  Their  disappearance  may 
have  been  due  to  the  aridity  of  the  period  which  culminated  in  the  seventh  or  eighth 
centuries.  Then  the  village  people,  the  Pajaritans,  may  have  flourished  in  the  middle 
ages,  a  period  moister  than  the  present,  but  not  so  moist  as  the  preceding  propitious  epoch. 
They  may  have  been  ousted  by  the  twofold  disaster  of  prolonged  drought  and  fierce  invasion 
which  would  have  come  to  America  about  1200  or  1300  a.  d.  if  conditions  here  were  like 
those  of  Asia.  And  finally,  the  occupation  of  places  hke  Gran  Quivira  by  the  modern  Pueblo 
Indians  may  be  the  result  of  propitious  conditions  following  the  dry  period  of  the  thirteenth 
century.  Such  a  correlation  between  chmate  and  history  is  as  yet  merely  a  suggestive 
hypothesis,  but  it  may  well  be  kept  in  mind  in  future  investigations. 


SUPPLEMENTARY  STATEMENT. 

Since  the  preceding  chapter  was  prepared  for  the  press  there  has  come  to  hand  a  publication 
bearing  the  title  “  The  Physiography  of  the  Rio  Grande  Valley,  New  Mexico,  in  relation  to  Pueblo 
Culture,”  by  Edgar  Lee  Hewett,  Junius  Henderson,  and  Wilfred  William  Robbins,  Washington, 
1913.  The  last  thirty  pages  of  this  are  devoted  to  an  article  on  “  Climate  and  Evidence  of  Cli¬ 
matic  Changes,”  by  Junius  Henderson  and  Wilfred  W.  Robbins.  In  this  article  the  authors  in 
general  adopt  the  methods  set  forth  in  “Explorations  in  Turkestan”  and  in  “The  Pulse  of  Asia.” 
Their  work  was  apparently  completed  prior  to  the  appearance  in  1911  of  the  first  of  my  own 
articles  on  changes  of  climate  in  the  United  States.  Therefore,  their  conclusions  are  of  the  more 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


91 


value  because  they  were  reached  independently  and  without  knowledge  of  the  investigations 
described  in  this  volume.  They  quote  various  authors  for  and  against  changes  of  climate,  among 
whom  Lowe,  L.  F.  Ward,  Hewett,  Cummings,  Hoffman,  Morrison,  Newbury,  and  Blake  believe 
in  changes,  although  several  of  them  base  their  belief  on  very  slight  evidence.  On  the  other 
hand.  Holmes  speaks  doubtfully,  and  Cope,  Fewkes,  Mindeleff,  and  Bandelier  are  strongly  opposed 
to  the  idea.  None  of  these  authors,  however,  goes  into  the  question  exhaustively.  A  quotation 
from  Hewett*  in  regard  to  the  Pajarito  or  Jemez  Plateau  will  illustrate  the  extent  to  which  the 
subject  has  hitherto  been  investigated: 

“It  appears  that  the  abandonment  of  the  cliff  and  pueblo  villages  of  the  plateau  occurred  from 
600  to  800  years  ago  as  a  result  of  climatic  modifications  by  reason  of  which  the  hardships  of 
living  at  these  sites  became  unendurable.  The  transition  from  plateau  to  valley  life  was  not 
necessarily  sudden.  There  is  no  evidence  of  any  great  simultaneous  movement  from  all  parts  of 
the  plateau.  The  change  was  probably  accomplished  within  a  generation  or  two,  one  village 
after  another  removing  to  the  valley  or  to  more  distant  places,  as  the  desiccation  of  the  plateau 
proceeded.  There  is  at  present  not  a  single  stream  on  the  east  side  of  the  Jemez  Plateau  between 
the  Chama  and  the  Jemez  that  carries  its  water  to  the  Rio  Grande  throughout  the  year.  The 
ancient  Tewa  people  were,  as  are  their  modern  successors,  agriculturists;  hence,  their  living  was 
dependent  on  the  water-supply.  Only  the  most  primitive  style  of  irrigation  was  practised  and 
there  is  every  evidence  that  the  region  was  never  rich  in  game  or  natural  food  products  of  any 
kind.” 

Henderson  and  Robbins  take  up  the  matter  much  more  fully  than  their  predecessors.  Inas¬ 
much  as  their  work  centered  in  the  Pajarito  Plateau,  it  will  be  worth  while  to  quote  what  they  say 
as  to  the  Canon  de  los  Frijoles.f 

“The  ancient  ruins  in  the  canyon  itself  once  must  have  housed  some  hundreds  of  people  even 
if  all  the  ruins  were  not  inhabited  contemporaneously,  and  there  is  nothing  to  indicate  that  they 
were  not  practically  all  occupied  at  the  same  time.  Bandelier,  who  is  conservative,  places  the 
population  at  1,500.  In  addition,  the  ruins  of  old  dwellings  are  to  be  found  everywhere  on  the 
adjacent  mesas  and  scattered  throughout  the  other  canyons  which  cut  the  plateau.  The  mesa 
dwellings  are  not  so  situated  as  to  indicate  that  they  were  placed  on  elevated  ground  for  pro¬ 
tection  from  enemies,  and  it  seems  wholly  improbable  that  their  occupants  would  have  lived  in 
such  places  if  they  were  dependent  for  food  on  crops  in  the  canyons.  It  is  also  inconceivable 
that  they  would  have  lived  on  the  mesas  with  their  water-supply  in  the  bottoms  of  the  canyons, 
450  to  600  feet  below  them,  unless  the  canyons  were  already  occupied  and  their  tillable  land  was 
taken  up  by  others.  No  extensive  irrigation  works  on  the  mesas  have  yet  been  discovered  which 
would  provide  irrigation  for  crops,  and  carrying  water  for  irrigation  to  the  mesas  from  the  nearest 
present  sources  would  have  been  quite  impracticable,  yet  there  is  no  reason  to  believe  that  corn 
could  now  grow  on  the  mesas  in  the  vicinity  of  these  ruins.  The  country  is  not  and  probably  has 
not  been  rich  in  game.  It  is  difficult  to  believe  that  so  many  people  would  have  built  on  the 
mesas  unless  they  could  have  raised  crops  there  without  irrigation.  With  fertile  valleys,  good 
water,  and  better  opportunities  in  the  bottoms  of  the  canyons  for  protection  and  seclusion  from 
enemies,  it  seems  very  much  more  likely  that  they  would  have  occupied  the  valleys  alone  unless 
there  were  more  inhabitants  than  the  limited  valley  areas  would  support.  Hence  a  logical  con¬ 
clusion  is  that  probably  most  of  the  dwellings  in  the  canyons  and  on  the  mesas  were  occupied 
simultaneously  at  some  period.  The  fact  that  it  was  not  necessary  to  live  near  the  fields  would 
hardly  account  for  the  placing  of  the  homes  on  the  high,  dry  mesas,  because  locating  them  here 
would  add  to  the  distance  and  altitude  to  which  the  grain  and  water  must  be  carried.  It  is  also 
wholly  improbable  that  any  great  number  of  springs  was  destroyed  by  earthquakes  or  concealed 
by  the  inhabitants  on  abandoning  the  dwellings,  without  many  of  them,  or,  indeed,  most  Pf  them, 
revealing  themselves  now  by  seepage,  while  if  destroyed  by  desiccation,  that  would  put  an  end 
to  them  and  stop  seepage. 

“If  there  has  been  progressive  desiccation  of  the  region  it  would  be  fully  adequate  to  account 
for  the  abandonment  of  these  ruins  by  the  rather  large  population  which  probably  once  occupied 
them.  Then,  inasmuch  as  the  same  condition  is  found  over  a  very  large  area,  indicating  that 
in  the  whole  now  arid  region  the  aggregate  population  must  have  been  very  great,  the  question 
would  arise,  where  did  they  go?  It  is  not  sufficient  to  say  merely  that  they  were  driven  out. 


*  Hewett,  Edgar  L.:  Antiquities  of  the  Jemez  Plateau,  New  Mexico,  Bull.  32,  Bur.  Amer.  Ethn.,  p.  13,  1906. 
t  Hewett,  Henderson,  and  Robbins:  Physiography  of  the  Rio  Grande  Valley,  pp.  53,  55,  and  56. 


92 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


A  general  migration  to  some  distant  region  where  conditions  are  more  favorable  would  probably 
have  left  a  well-defined  trail  in  the  traditions  of  the  whole  region.  Numerous  traditions  of  local 
migrations  are  known,  but  all  should  be  scanned  with  care  before  acceptance.  It  seems  to  the 
authors  that  a  much  more  reasonable  explanation  of  the  known  phenomena  is  this:  If  the  rainfall 
slowly  decreased,  conditions  must  have  become  very  gradually  more  severe.  More  and  more 
frequent  droughts  and  accompanying  starvation  periods  would  result,  during  which  the  weaker 
members  of  the  tribe  would  perish,  not  altogether  from  starvation,  but  from  the  reduction  of 
their  powers  of  resistance  to  disease,  cold,  and  other  hardships  through  want  of  sufficient  nourish¬ 
ment.  Thus  the  general  physique  of  the  tribe  would  be  preserved  by  the  weeding  out  of  the 
unfit  instead  of  weakening  the  physique  of  the  tribe  as  a  whole.  As  the  severity  of  such  droughts 
increased  it  is  probable  that  minor  wars  for  the  possession  of  the  small,  better-watered  tracts  would 
occur,  still  further  reducing  the  various  tribes  and  decreasing  the  aggregate  population  of  the 
region.  Occasional  minor  epidemics  would  be  apt  to  reduce  still  further  their  numbers,  especially 
if  they  occurred  during  periods  of  drought.  Thus  it  is  reasonable  to  suppose  that  as  a  natural 
result  of  desiccation  the  population  decreased  so  gradually  that  the  decline  could  be  discovered 
only  by  very  accurate  statistical  records  or  by  a  general  comparison  of  the  numbers  living  in  the 
region  at  widely  separated  periods.  In  this  way  the  depopulation  would  progress  slowly  by 
natural  processes  and  therefore  would  not  attract  the  attention  of  the  inhabitants  and  would 
leave  little  impression  in  their  legends  or  traditions.  The  remnant  of  the  population  would 
gradually  move  in  small  bands  to  situations  favorable  to  agricultural  pursuits,  thus  becoming 
widely  dispersed.  The  foregoing  changes  would  be  expected  to  occur  in  a  region  which  was 
slowly  drying  up,  and  present  conditions  are  just  such  as  one  would  be  led  to  expect.  Hence  it 
seems  very  probable  from  the  archeologic  evidence  that  there  has  been  progressive  desiccation.” 

It  is  interesting  to  find  that  in  the  publication  under  discussion  botanical  evidence  receives 
considerable  attention,  one  of  the  joint  authors.  Professor  Robbins,  being  a  botanist.  On  page  56 
he  discusses  a  matter  of  considerable  importance.  My  own  notes  contain  many  references  to 
phenomena  identical  with  those  he  describes,  although  I  have  not  discussed  them  so  far  as  New 
Mexico  is  concerned  for  the  same  reason  which  makes  Professor  Robbins  hesitate,  that  is,  because 
the  number  of  exact  observations  is  limited;  yet  the  fact  that  his  observations  and  my  own 
agree  so  closely  adds  to  their  value.* 

“While  it  is  true  that  during  3,000  years  some  species  may  be  altered  to  a  slight  extent,  others 
may  be  introduced  by  various  means,  and  others  may  come  into  existence  suddenly  (mutation), 
and  that  the  relations  of  formations  and  associations  of  plants  may  have  changed  in  some  measure, 
yet  it  is  highly  improbable  that  there  has  been  a  marked  and  widespread  modification  of  the 
flora  within  that  time.  However,  the  relation  of  the  two  principal  plant  formations  of  the  region 
seems  to  afford  some  evidence  of  progressive  climatic  change.  This  may  be  seen  in  the  stress 
zone  between  the  pinon  pine-cedar  formation  and  the  rock-pine  formation.  Pinon  pines  and 
cedars  grow  in  drier  situations  than  do  rock  pines.  In  the  area  under  discussion  rock  pine  occurs 
on  the  higher  parts  of  the  mesas,  back  toward  the  mountains,  while  pinon  pine  and  cedar  are 
confined  to  the  lower  portions,  down  toward  the  rim  of  the  Rio  Grande  Canyon.  At  a  distance 
of  1  to  3  miles  back  from  the  Rio  Grande  the  two  formations  meet  and  here  there  is  a  battle  for 
occupancy  of  space.  If  in  this  struggle  between  these  two  plant  formations  the  pinon  pine-cedar 
formation  is  the  successful  competitor  and  gradually  encroaches  on  the  rock-pine  formation,  and 
if  such  encroachment  is  widespread,  this  condition  probably  indicates  progressive  desiccation  of 
the  country.  That  is  the  condition  in  this  region.  If  the  rock-pine  formation  were  extending  into 
the  territory  of  the  formation  below  it,  there  would  be  rock-pine  seedlings  as  outposts  of  the 
invasion,  and  their  presence  would  be  evidence  that  conditions  in  the  new  territory  were  favorable 
for  their  growth.  From  the  lower  extension  of  the  formation  rock-pine  seedlings  are  almost 
entirely  absent.  The  outermost  individuals  are  large  trees,  in  many  cases  the  largest  of  the 
formation,  possibly  several  centuries  old,  indicating  that  in  the  early  stages  of  their  growth 
conditions  were  more  favorable  for  the  species  to  obtain  a  .start  and  that  no  such  favorable  period 
has  occurred  since.  Pinon-pine  and  cedar  seedlings  do  occur  at  the  stress  zone,  although  not  in 
greater  abundance  than  at  any  other  point  in  the  formation.  The  whole  aspect  of  the  line  of 
stress  between  these  two  formations  shows  that  the  pinon  pine-cedar  formation  is  encroaching 
on  the  rock-pine  formation,  a  condition  which  would  not  exist  unless  there  is  progressive  desicca¬ 
tion  which  is  tending  to  make  the  debatable  territory  unfavorable  for  the  rock  pines  and  better 
suited  for  pinon  pines  and  cedars.” 


*  Robbins:  Physiography  of  the  Rio  Grande  Valley,  p.  56. 


SUCCESSIVE  STAGES  OF  CULTURE  IN  NORTHERN  NEW  MEXICO. 


93 


The  final  conclusions  of  Professors  Henderson  and  Robbins  are  summed  up  in  twelve  state¬ 
ments,  part  of  which  refer  to  geological  matters  whose  relation  to  man  has  not  been  definitely 
determined.  The  others  are  as  follows  (pp.  68-9) : 

“1.  The  climate  of  the  Rito  de  los  Frijoles  and  surrounding  region  does  not  now  permit  the 
raising  of  corn  without  irrigation  except  in  perhaps  a  few  favored  localities. 

“3.  It  would  not  require  a  very  great  increase  in  precipitation  to  make  the  raising  of  hardy, 
drought-resisting  varieties  of  corn  possible  without  irrigation  in  localities  where  it  is  not  now 
possible. 

“4.  Distribution  and  extent  of  ruins  throughout  the  Southwest,  including  the  Jemez  Plateau, 
strongly  suggest  different  conditions  a  few  centuries  ago,  "svith  a  more  general  distribution  of 
springs  and  streams  and  sufficient  precipitation  for  the  cultivation  of  areas  not  now  fit  for  agri¬ 
culture  and  for  the  irrigation  of  tracts  where  it  is  now  impracticable,  thus  indicating  a  probable 
change  of  climate  within  at  most  the  last  ten  to  twenty  centuries.  There  is  some  direct  historical 
evidence  pointing  the  same  way. 

“7.  There  is  some  botanical  evidence,  although  meager,  of  a  change  in  climate  within  four  or 
five  centuries  and  of  the  still-continuing  desiccation. 

“8.  On  the  whole,  in  the  opinion  of  the  writers,  various  lines  of  evidence  point  to  progressive 
desiccation  of  the  region  since  the  beginning  of  the  pueblo  and  cliff-dwelling  period,  with  no 
important  evidence  inconsistent  with  this  view,  although  the  change  in  population  may  possibly 
be  ascribed  to  other  causes. 

“9.  This  progressive  desiccation,  if  it  has  occurred,  doubtless  has  been  accompanied  by 
numerous  slight  fluctuations  in  climatic  conditions,  just  such  as  are  matters  of  record  during 
historic  time,  wet  and  dry  and  warm  and  cool  cycles  alternating. 

“12.  Evidence  of  recent  desiccation  is  not  conclusive,  but  the  problem  is  probably  capable  of 
solution  by  further  cooperative  investigation  along  lines  suggested  in  this  discussion.  Several 
lines  of  evidence  point  to  slight  progressive  desiccation  in  the  Southwest  within  the  period  of 
human  occupancy.  Such  desiccation  would  satisfactorily  account  for  present  conditions,  and  no 
other  explanation  yet  suggested  seems  adequate.” 

On  the  whole,  the  conclusions  of  Professors  Henderson  and  Robbins  as  well  as  of  Dr.  Hewett 
agree  with  those  to  which  we  have  been  led  in  the  volume.  This  agreement  is  important,  inas¬ 
much  as  their  publication  is  the  first  in  which  independent  workers  other  than  the  present  author 
have  taken  up  the  methods  discussed  in  this  volume  and  have  applied  them  to  a  region  in  America. 


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CHAPTER  X. 


SOUTHERN  MEXICO  AS  A  TEST  CASE. 

The  testing  of  a  theory  can  be  accomplished  in  at  least  three  ways.  First,  it  can  be 
applied  to  new  regions;  second,  it  can  be  confronted  by  new  lines  of  evidence;  and,  finally, 
it  can  be  investigated  by  new  observers  employing  different  methods  or  at  any  rate  coming 
to  the  problem  from  a  different  point  of  view.  In  the  present  investigation  we  have 
already  used  the  Southwest  as  a  new  region  to  be  compared  with  the  old  regions  of  Asia 
and  the  lands  of  the  Mediterranean.  Let  us  now  take  still  a  third  great  region  and  once 
more  make  a  test.  Southern  Mexico  lies  at  a  distance  of  from  1,200  to  1,500  miles  from 
Arizona  and  New  Mexico.  This  is  a  small  matter  compared  with  the  8,000  or  10,000  miles 
which  separate  those  regions  from  the  parts  of  Asia  where  our  chief  conclusions  as  to 
that  continent  were  reached.  Nevertheless,  the  difference  between  Arizona  and  southern 
Mexico  is  greater  than  between  Arizona  and  Turkestan.  This  is  because,  although  Arizona 
has  summer  rain  like  that  of  Mexico,  its  most  important  precipitation  is  the  winter  type 
characteristic  of  the  zone  where  westerly  winds  and  subtropical  aridity  are  the  dominant 
features  of  winter  and  summer  respectively.  In  going  from  Arizona  to  southern  Mexico, 
on  the  contrary,  we  cross  the  trade-wind  zone  and  enter  the  edge  of  the  zone  of  equatorial 
rains  and  calms.  Hence  we  are  able  to  subject  our  theories  to  a  more  severe  test  than 
would  be  possible  even  if  we  completely  encircled  the  globe,  but  remained  in  the  same 
zone  of  climate.  The  change  is  so  great  that  we  are  able  not  only  to  test  our  theory  in  a 
distinctly  new  region,  but  also  to  confront  it  with  certain  new  lines  of  evidence. 

The  investigations  in  Mexico  to  be  described  below  were  made  during  the  spring  of 
1912.  Those  here  discussed  were  confined  chiefly  to  the  City  of  Mexico,  in  latitude  19.5°, 
and  to  Oaxaca  and  Mitla,  in  latitude  16°.  In  both  of  these  places  evidences  of  changes 
of  climate  appeared  to  an  unexpected  degree.  In  discussing  this  matter,  let  us  take  up, 
first,  the  recent  fluctuations  of  the  lakes  near  the  City  of  Mexico;  second,  the  evidences 
of  a  change  in  the  conditions  of  the  Basin  of  Mexico  during  the  time  of  ancient  civiliza¬ 
tions;  and  third,  the  alluvial  terraces  found  near  Mexico  and  in  Oaxaca.  A  fourth  type 
of  evidence,  namely,  the  peculiar  location  of  the  ruins  of  Yucatan,  together  with  those  of 
Guatemala  and  Honduras,  is  so  new  and  important  that  it  will  be  left  for  later  chapters 
after  we  have  considered  the  trees  of  California. 

In  the  Monthly  Weather  Review,  for  November  1908,  I  have  discussed  the  City  of 
Mexico  and  Lake  Tezcuco  in  their  relation  to  changes  of  climate.  In  considering  this 
matter  here,  I  shall  largely  follow  that  article,  but  shall  add  new  facts  which  have  come 
to  hght  since  it  was  written.  The  City  of  Mexico  lies  7,400  feet  above  the  sea  near  the 
salt  lake  of  Tezcuco  and  the  tributary  fresh  lakes  of  Xochimilco  and  others.  The  basin 
containing  these  lakes  is  similar  in  its  general  features  to  that  of  the  Great  Salt  Lake  in 
Utah,  Lop  Nor  in  Central  Asia,  and  Seistan  in  Eastern  Persia.  Accurate  historic  records 
of  the  country  extend  back  to  the  time  of  the  Spanish  invasion  in  1519,  and  before  that  we 
have  fairly  reliable  traditions  for  at  least  200  years  more.  Taking  merely  the  600  years 
for  which  we  now  have  data,  we  find  that  during  that  time  there  appears  to  have  been  a 
slight  but  appreciable  change  of  chmate  in  Mexico  similar  to  that  which  has  apparently 
occurred  in  Asia.  The  evidence  is  somewhat  masked  because  the  natural  course  of  events 
has  been  interrupted  by  various  works  of  man,  such  as  the  dikes,  canals,  and  tunnels 
which  have  been  built  since  1446  to  regulate  the  waters  of  Tezcuco  and  its  three  tributary 

95 


96 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


lakes.  Nevertheless,  there  have  been  certain  periods  when  nature  has  triumphed  over 
human  endeavor  and  the  waters  have  returned  to  the  level  which  they  would  naturally 
occupy  if  man  had  never  interfered.  A  comparison  of  the  chief  epochs  of  this  sort  seems 
to  afford  some  ground  for  the  behef  that  the  chmate  of  Mexico  has  passed  through  fluctu¬ 
ations  like  those  of  Asia,  on  the  one  hand,  and  of  more  northern  regions  in  America,  such 
as  California  and  New  Mexico,  on  the  other  hand. 

The  great  authority  on  early  Mexico  is  Humboldt,  whose  “Essai  Politique  sur  la 
Royaume  de  la  Nouvelle-Espagne”  was  published  in  1811  as  the  third  part  of  the  ‘‘Voyage 
de  Humboldt  et  Bonpland.”  Later  and  less  authoritative  writers,  such  as  Prescott  and 
Romero,  follow  him  closely,  adding  little  that  is  new.  Humboldt  specifically  states  his 
belief  that  the  climate  of  Mexico  in  his  day  was  more  arid  than  it  was  at  the  time  of  the 
founding  of  the  capital  about  1325  a.  d.  He  attributes  the  change  in  part  to  undefined 
meteorological  causes  whereby  evaporation  has  exceeded  precipitation,  and  in  part  to  the 
reckless  destruction  of  forests  by  the  Spaniards.  He  is  sure  that  the  level  of  Lake  Tezcuco 
has  fallen,  through  natural  causes  as  well  as  through  the  works  of  man,  and  cites  this  fact 
as  the  chief  evidence  of  a  change  of  climate. 

According  to  tradition,  the  Aztec  founders  of  Mexico,  like  most  of  the  world’s  great 
races,  came  from  the  north.  After  a  century  of  adventurous  wanderings,  enlivened  by 
the  vicissitudes  of  war,  conquest,  and  slavery,  they  appear  to  have  reached  the  shores  of 
Lake  Tezcuco  about  1325  a.  d.  Hoping  for  peace  and  safety,  they  located  themselves  on 
some  small  islets  several  miles  from  the  shore.  There  they  laid  the  foundations  of  the 
present  proud  City  of  Mexico  by  sinking  piles  into  the  marshy  shallows  and  erecting  upon 
them  light  huts  of  reeds  and  rushes  above  the  reach  of  the  water.  During  the  succeeding 
century,  according  to  Humboldt,  the  city  grew  and  prospered  and  its  rule  spread  over 
the  neighboring  regions.  It  was  still  an  island  city  with  houses  on  piles,  with  canals 
instead  of  streets  in  many  cases,  and  with  canoes  in  place  of  beasts  of  burden.  Sometimes 
it  suffered  when  the  lake  rose  more  than  usual.  The  first  well-authenticated  event  of  this 
kind  is  recorded  by  Torquemada,*  a  monk  who  hved  in  Mexico  from  the  middle  of  the 
sixteenth  century  well  into  the  seventeenth.  It  happened  in  the  early  years  of  the  reign 
of  Montezuma,  who  became  king  in  1436  a.  d.  In  this  year  the  water  “submerged  the  whole 
city  and  the  inhabitants  travelled  in  canoes  and  barques,  without  knowing  how  to  remedy 
matters  nor  how  to  defend  themselves  from  so  great  an  inundation.  ”  The  next  year  was 
also  phenomenal,  and  Torquemada  enlarges  on  the  abundant  crops  and  great  prosperity, 
which,  he  says,  are  affirmed  by  all  historians.  At  about  this  time  the  first  known  dike  was 
built  in  the  year  1446  a.  d.  If  it  were  not  for  Torquemada’s  direct  statement  as  to  the 
great  rain  and  abundant  crops  we  might  suppose  that  the  dike  happened  to  be  built  then 
merely  because  of  an  advance  in  the  art  of  engineering;  or  because  the  increasing  number 
of  buildings  in  the  city  caused  the  land  to  settle,  as  it  has  done  in  recent  years,  when  the 
erection  of  the  new  National  Theater,  for  instance,  has  caused  a  local  subsidence  of  4  or 
5  feet  which  is  evident  to  the  most  casual  observer  by  reason  of  the  warping  of  the  pavements 
of  the  streets.  It  seems  probable,  however,  that  the  building  of  the  dike  was  due  more  to 
chmate  than  to  any  other  cause,  for  the  water  did  not  remain  at  a  high  level  thereafter,  but 
near  the  end  of  the  fifteenth  century,  fell  so  low  that  the  city  suffered  much  distress  because 
canoes  laden  with  supphes  of  food  could  not  come  in  as  formerly  from  the  surrounding 
country.  When  Cortez  came  to  Mexico  in  1519  the  water  had  again  risen  and  the  capital 
was  still  a  western  Venice.  He  describes  it  as  located  on  an  island  two  leagues  from  the 
mainland.  In  order  to  besiege  it  effectively  he  was  obliged  to  build  brigantines,  and  in  these 
he  was  able  to  sail  completely  around  the  city,  except  for  a  small  distance  on  the  southwest 

*  Fray  Juan  de  Torquemada:  Los  Veinte  i  vn  Libros  Rituales  y  Monarchia  Indiana,  etc.,  etc.  Edition  of  1723.  (The 
original  edition  is  1615.)  Book  ii,  Chap,  xxxvir,  p.  157.  For  these  references  to  variations  in  Mexican  lakes,  I 
am  indebted  to  the  researches  of  Mr.  Adolph  Bandeher. 


SOUTHERN  MEXICO  AS  A  TEST  CASE. 


97 


side  toward  Chapultepec,  where  the  water  was  too  shallow.  The  small  boats  engaged  in 
ordinary  traffic  sailed  everywhere,  however,  not  only  on  Tezcuco,  but  on  the  other  lakes 
and  on  the  connecting  rivers.  It  is  not  evident  whether  this  was  a  permanent  condition, 
but  in  1553,  as  appears  below,  we  have  evidence  of  a  special  inundation. 

Two  or  three  generations  after  the  Spanish  conquest  the  condition  of  the  City  of  Mexico 
had  changed.  It  had  ceased  to  be  an  island,  the  canals  had  become  dry,  and  wheeled 
vehicles  had  taken  the  place  of  canoes.  This  result  was  due  in  part  to  the  construction 
of  additional  dikes,  but  nature  apparently  had  been  the  main  agent  in  the  matter.  Such 
seems  to  have  been  the  opinion  of  Torquemada.  He  is  quoted  by  Prescott  (page  33) : 

“As  God  permitted  the  waters  which  had  once  covered  the  whole  earth  to  subside,  after  man¬ 
kind  had  been  nearly  exterminated  for  their  iniquities,  so  He  allowed  the  waters  of  the  Mexican 
lake  to  subside  in  token  of  good  will  and  reconciliation  after  the  idolatrous  races  of  the  land  had 
been  destroyed  by  the  Spaniards.” 

The  waters  rose  again,  however,  for,  to  quote  Torquemada,*  “in  this  same  year  1604, 
it  rained  so  much  in  the  month  of  August  that  the  lake  of  Mexico  was  filled  with  all  its 
plains,  so  that  the  waters  covered  nearly  all  the  city  and  reached  such  a  point  in  some 
streets  that  people  passed  in  canoes,  and  I  myself  passed  San  Juan  in  this  manner.  The 
inhabitants  hved  carelessly,  and  forgetful  of  the  previous  danger  of  the  same  kind  in  the 
year  1553  when  Don  Luis  de  Velasco,  the  First,  was  governor.  ...”  This  wet  period 
continued,  for  we  are  told  that  in  1607  the  town  of  Tultitlan  was  inundated  for  the  third 
time  with  great  loss  of  houses  and  fields.  To  prevent  such  occurrences  in  the  future  a  tunnel 
was  built  to  carry  off  the  surplus  water  of  the  Cuautitlan  River.  It  might  be  supposed 
that,  after  the  construction  of  the  tunnel,  the  lake  would  never  return  to  its  natural  condi¬ 
tion.  In  1629,  however,  during  a  season  of  uncommonly  heavy  floods,  the  tunnel  was 
stopped  up  completely.  The  City  of  Mexico  was  flooded  for  a  time  and  was  in  great  straits 
during  a  period  of  rainy  years  lasting  till  1634.  Thereafter  it  became  dry  once  more, 
although  neither  the  tunnel  nor  the  old  dikes  were  in  a  condition  to  prevent  the  rise  of  the 
water.  Again,  from  1675  to  about  1755,  the  tunnel  was  closed,  being  filled  with  earth  for 
an  unknown  distance.  At  the  same  time  also  the  dikes  were  in  poor  repair,  breaking 
whenever  the  water  rose  higher  than  usual;  yet  the  city  continued  to  stand  on  dry  land, 
though  sometimes  a  year  of  exceptional  rains  caused  the  water  to  rise  sufficiently  to  flow 
into  some  of  the  streets,  but  not  enough  to  do  any  serious  damage.  Taken  as  a  whole 
the  history  of  the  lake  appears  to  have  been  characterized  by  fluctuations  of  considerable 
magnitude.  How  far  these  fluctuations  agree  with  those  in  regions  farther  north  will 
appear  in  a  later  chapter  after  we  have  considered  the  data  derived  from  trees. 

The  evidence  just  presented  is  in  itself  too  slight  to  justify  any  conclusion  derived 
from  it  alone.  Only  by  bringing  together  many  diverse  fines  of  evidence  can  we  ascertain 
the  truth  even  approximately.  Fortunately,  Mr.  Manuel  Gamio,  under  the  direction  of 
Professor  Franz  Boas,  has  recently  been  engaged  in  archeological  excavations  on  behalf 
of  the  International  School  of  American  Archeology  and  Ethnology,  and  has  done  some 
work  which  is  significant  for  our  present  purpose.  The  hamlet  of  San  Miguel  Amantala, 
near  the  village  of  Azcapotzalco,  lies  on  the  edge  of  the  lacustrine  plain  of  the  City  of 
Mexico,  not  far  from  the  base  of  the  hills  on  the  west.  This  portion  of  the  plain  is  dotted 
with  little  mounds  which  mark  the  sites  of  villages  or  small  groups  of  houses  built  by  the 
Aztecs  and  full  of  the  typical  pottery,  images,  and  other  relics  of  that  people.  Elsewhere 
the  plain  is  strewn  with  the  scattered  fragments  of  another  and  older  type  of  civilization, 
which  is  known  as  that  of  San  Juan  Teotihuacan,  from  the  great  pyramids  of  that  name 
on  the  eastern  border  of  the  basin  of  Mexico.  The  San  Juan  relics  never  occur  in  mounds 
of  the  Aztec  type  except  for  a  few  stray  bits  which  have  been  carried  in  by  accident.  This 
indicates  that  the  two  are  of  distinctly  different  dates,  as  indeed  we  know  from  other 


8 


*  Loc.  cit.  Book  v,  Chap,  lx,  p.  728  b;  and  Chap,  lxx,  p.  756. 


98 


THE  CLIMATIC  FACTOE  AS  ILLUSTEATED  IN  AEID  AMEEICA. 


evidence.  Some  of  the  mounds  of  Aztec  age  appear  to  be  merely  accumulations  of  earth 
from  the  adobe  roofs  and  walls  of  the  ancient  dwellings,  but  others  appear  to  have  been 
built  of  set  purpose.  This  suggests  that  for  some  reason  the  earlier  people  built  their 
houses  directly  upon  the  plain,  while  the  later  Aztecs  raised  theirs  upon  mounds.  To 
Professor  Boas  this  fact  seems  to  indicate  merely  that  before  coming  to  the  Mexican 
plateau  the  Aztecs  had  probably  acquired  the  habit  of  building  elevated  structures  and  that 
this  persisted  throughout  their  history.  Possibly,  however,  the  elevation  was  an  advantage 
for  purposes  of  defense;  or  perhaps,  at  the  coming  of  the  Aztecs,  the  level  of  the  lakes  was 
so  high  that  in  times  of  unusual  rain  the  villages  were  occasionally  in  danger  of  inundation, 
although  during  the  days  of  their  predecessors,  the  San  Juan  people,  the  plain  may  have 
been  so  dry  that  no  such  danger  existed. 

In  one  of  the  sites  marked  by  San  Juan  pottery  Professor  Boas  has  made  an  excavation 
in  which  he  finds  the  following  section  from  the  top  downward: 

(A)  1  or  2  feet  of  fine,  dark  surface  soil  full  of  bits  of  San  Juan  pottery. 

(B)  6  inches  to  2  feet  of  “tepetate,”  or  “caliche”  as  it  is  called  farther  north,  in  layers  from 
1  inch  to  1  foot  in  thickness.  It  is  mixed  with  bits  of  San  Juan  pottery,  and  is  interstratified  with 
layers  of  well-rounded  gravel  containing  pebbles  up  to  2  or  3  inches  in  diameter.  The  “tepetate” 
is  a  white  calcareous  deposit  which  is  frequently  formed  in  dry  regions  where  a  large  amount  of 
water  evaporates.  It  is  usually  considered  characteristic  of  rather  arid  conditions.  Here  at 
Azcapotzalco  it  is  frequently  faulted  a  few  inches,  as  if  the  ground  had  sunken  a  little. 

(C)  4  or  5  feet  of  “culture  layers”  full  of  San  Juan  pottery  intermingled  with  ashes,  fire¬ 
places,  and  the  foundations  of  ancient  houses. 

(D)  5  or  6  feet  of  fine  sand,  often  in  pockets  or  in  slightly  cross-bedded  bands.  This  is  inter¬ 
mixed  with  finer  sandy  materials  and  a  certain  amount  of  clay  like  that  which  forms  the  bulk  of 
the  overlying  culture  layers.  Fragments  of  pottery  of  the  same  San  Juan  type,  together  with 
bones  and  angular  stones  as  much  as  a  foot  in  diameter,  indicate  that  men  lived  here  when  the 
layers  were  being  laid  down,  although  there  are  no  foundations. 

(E)  11  or  12  feet  of  gravel  and  sand  growing  coarser  downward,  and  at  the  base  containing 
cobble-stones  several  inches  in  diameter.  The  pebbles  are  mostly  well  rounded,  as  if  they  had  been 
carried  far  in  running  water,  although  a  few  angular  pieces  are  found,  especially  in  the  more 
clayey  portions  of  the  sand.  San  Juan  pottery  occupies  the  upper  5  or  6  feet,  but  only  in  small 
quantities.  The  fragments  are  often  angular,  showing  that  they  have  not  been  carried  far  in  running 
water.  The  lower  5  or  6  feet  contain  quite  a  different  kind  of  pottery,  belonging  apparently  to 
the  type  which  Professor  Boas  has  called  the  Mountain  culture.  It  is  much  more  archaic  than  the 
San  Juan  or  Aztec  types,  and  it  is  certainly  older,  since  it  lies  lower.  Whether  it  persisted  until 
the  time  of  the  later  cultures  we  can  not  tell.  Professor  Boas  says  that  as  yet  it  has  nowhere  been 
found  on  the  surface  of  the  plain,  although  it  is  common  in  small  areas  scattered  among  the  sur¬ 
rounding  mountains.  Hence  its  name.  The  pieces  found  by  Professor  Boas  in  his  excavations 
were  all  well  rounded,  showing  that  they  had  been  carried  some  distance  by  running  water  or, 
in  other  words,  that  they  had  been  brought  in  from  the  mountains. 

At  a  short  distance  from  the  main  excavation  Professor  Boas  found  that  the  gravels  of  this 
formation  die  out.  Minor  excavations  in  several  places  led  him  to  conclude  that  the  main  gravel 
just  described  indicates  the  location  of  a  river  bed  less  than  100  meters  wide  and  extending  in  a 
north-and-south  direction.  Outside  the  river  bed,  but  at  the  same  level,  the  coarseness  of  the 
decomposed  tufaceous  matter  increases  a  little,  and  the  material  is  more  sandy  than  above  or  below, 
indicating  sorting  by  moving  water.  In  the  sandy  material  the  archaic  pottery  of  the  Mountain 
culture  is  found  in  large  amounts.  It  is  not  stream-worn  or  rounded,  and  the  paints  with  which 
it  is  decorated  are  still  fresh.  Clearly  it  has  not  been  carried  far,  which  indicates  that  the  plain 
near  the  old  river,  or  torrent,  must  have  been  inhabited.  Whether  this  pottery  is  of  the  same  age 
as  the  worn  fragments  in  the  river  bed  is  uncertain.  It  may  be  younger,  for  Professor  Boas  thinks 
that  there  may  have  been  a  gradual  transition  from  the  Mountain  culture  to  that  of  Teotihuacan. 

(F)  At  the  base  of  the  gravels  a  dark,  compact  clay  is  found  to  a  depth  of  about  7  feet.  It 
contains  almost  no  sand,  but  is  full  of  plant  remains,  and  of  hydrated  iron  which  stains  it  yellow. 
The  formation  looks  like  the  deposit  of  a  swamp  or  of  the  edge  of  a  lake.  It  is  sharply  separated 


SOUTHERN  MEXICO  AS  A  TEST  CASE. 


99 


from  the  overlying  gravel  in  a  way  to  suggest  a  drying  up  of  the  swamp  and  a  sudden  bringing 
in  of  materials  by  streams  which  had  formerly  had  their  mouths  nearer  the  mountains.  So  far 
as  the  clays  have  yet  been  studied  they  contain  no  pottery  or  other  evidences  of  human  occupation. 

(G)  Finally,  the  lowest  formation  thus  far  penetrated  is  a  light-colored  sand  which  Professor 
Boas  thinks  to  be  lacustrine. 

The  single  section  here  given  is  of  course  inconclusive.  The  transition  from  one  type 
of  deposits  to  another  may  have  arisen  from  a  change  in  the  course  of  streams  by  reason 
of  an  earthquake  or  volcanic  eruption,  or  it  may  have  been  due  to  a  tilting  of  that  particular 
portion  of  the  earth’s  crust.  The  full  history  of  the  basin  of  Mexico  can  be  ascertained 
only  by  means  of  a  large  number  of  excavations  well  scattered  over  the  whole  area.  Never¬ 
theless,  the  present  section  is  important.  Our  purpose  in  Mexico,  it  will  be  remembered, 
is  not  to  build  up  a  new  theory,  but  to  test  one  which  is  founded  upon  a  great  number  of 
facts  in  widely  scattered  parts  of  both  Asia  and  America.  We  want  to  discover  whether 
new  facts  found  in  other  regions  disagree  with  the  theory  and  compel  us  to  modify  it,  or 
agree  and  allow  us  to  carry  it  into  still  other  fields.  Hence  it  is  important  to  see  that  in 
this  particular  case,  the  only  one  of  its  kind  where  a  rigorous  test  is  yet  possible  in  this 
particular  region,  the  facts  agree  closely  with  what  would  be  expected  if  the  climate  of 
Mexico  has  varied  in  harmony  with  what  seems  to  have  been  the  case  in  other  parts  of 
the  world.  The  apparently  lacustrine  deposits  of  (G),  and  the  swampy  deposits  of  (F),  to 
begin  with  the  oldest  formation,  suggest  conditions  of  decided  moisture  with  such  an 
expansion  of  the  lakes  that  the  floor  of  the  basin  was  uninhabitable  and  the  people  were 
forced  to  live  in  the  surrounding  hills  where  they  developed  their  mountain  culture.  The 
succeeding  gravels  suggest  a  change  to  drier  conditions  whereby  the  shore  of  the  swamp  or 
lake  retreated  and  streams  began  to  encroach  upon  the  old  water-covered  bed.  At  the 
same  time  the  death  of  vegetation  upon  the  mountain  slopes,  because  of  the  aridity,  would 
permit  the  floods  to  wash  down  large  amounts  of  coarse  gravel,  with  which  would  be 
mingled  rounded,  waterworn  bits  of  pottery  from  the  mountain  villages,  as  appears  in 
the  lower  part  of  formation  (E).  During  this  dry  time,  if  such  it  really  were,  the  people 
of  the  mountain  type  apparently  expanded  from  their  restricted  habitat  among  the  arid 
hills,  and  spread  out  over  the  relatively  moist  plain  as  is  indicated  by  the  unworn  pottery 
at  the  base  of  (E)  in  the  portions  of  that  formation  outside  the  river  channel.  A  little  later, 
the  San  Juan  culture,  perhaps  that  of  an  invader,  made  its  appearance,  the  village  in 
question  being  close  to  the  base  of  the  mountains,  or  on  the  very  edge  of  the  plain,  as  is  indi¬ 
cated  by  the  fact  that  its  pottery  is  present  in  the  gravels,  but  is  free  from  marks  of  wear  by 
running  water.  By  the  time  that  deposit  (D)  began  to  be  laid  down  the  San  Juan  people 
were  hving  not  far  from  the  site  of  the  excavations.  When  (C)  was  being  formed  conditions 
were  very  much  as  now.  (B),  on  the  contrary,  with  its  layers  of  “tepetate”  and  gravel, 
suggests  a  return  toward  aridity,  while  (A)  brings  us  back  to  the  present  conditions.  If  the 
elevation  of  the  Aztec  mounds,  built  since  the  deposition  of  (A),  really  has  anything  to  do 
with  the  danger  of  flooding  it  may  indicate  a  slightly  moister  time  such  as  that  of  which 
the  traditions  give  a  suggestion  in  the  fourteenth  century,  while  now  in  the  nineteenth 
and  twentieth  centuries  we  are  back  once  more  in  dry  times.  The  whole  importance  of 
the  line  of  reasoning  here  followed  is  quite  independent  of  the  fact  that  the  specific  phe¬ 
nomena  here  described  are  subject  to  other  possible  explanations.  It  lies  rather  in  the 
fact  that  the  explanation  here  offered  harmonizes  with  a  vast  number  of  other  facts,  both 
in  Mexico  and  elsewhere,  while  the  other  explanations  take  little  account  of  anything 
outside  of  the  narrow  range  of  the  phenomena  immediately  to  be  described. 

Turning  now  from  archeology  and  lake-beds  to  alluvial  terraces,  we  find  that  the  kind 
discussed  in  previous  chapters  have  not  been  described  at  any  length  by  the  geologists  of 
Mexico.  Nevertheless,  they  are  said  to  be  abundant  in  the  states  of  Chihuahua,  Durango, 
and  elsewhere  in  the  northwest,  and  my  own  observation  proves  them  to  exist  in  large 


100 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


numbers  and  in  a  highly  developed  condition  in  Sonora,  and  also  in  the  vicinity  of  Monterey 
in  the  northeast  of  Mexico,  along  the  railway  line  from  Laredo  to  Mexico  City.  Through 
the  courtesy  of  Dr.  Jose  G.  Aguilera,  Director  of  the  Geological  Institute  of  Mexico,  one 
of  his  assistants,  Mr.  Ygnacio  S.  Bonillas,  was  permitted  to  spend  some  days  with  me  in 
studying  the  region  around  the  City  of  Mexico.  Thanks  to  Mr.  Bonillas’s  thorough 
knowledge  of  the  local  geology,  I  was  able  in  a  short  time  to  see  things  which  it  would 
have  taken  weeks  to  find  alone.  Northwest  of  the  city  the  volcanic  hills  are  deeply  seamed 
with  rugged  ravines  descending  from  high  mountains.  There  in  four  small  valleys  we 
found  terraces  of  the  kind  under  discussion.  The  presence  of  revolutionists  within  3  or 
4  miles  of  the  places  where  we  were  at  work,  and  in  all  the  country  round  about,  prevented 
us  from  examining  others  or  from  following  any  of  the  four  up  into  the  mountains,  where 
the  maximum  development  is  to  be  expected.  Nevertheless,  the  places  pointed  out  by 
Mr.  Bonillas  were  sufficient  to  indicate  that,  as  a  general  rule,  valleys  of  sufficient  size  and 
coming  from  mountains  of  sufficient  height  contain  alluvial  terraces  of  the  type  which 
elsewhere  seems  to  be  climatic.  In  various  places  the  cross-section  of  the  valleys  is  like 
that  shown  in  figure  8.  The  calcareous  caliche  or  ‘‘tepetate’’  on  the  top  of  the  main 

Fig.  8. — Cross-section  of  Alluvial  Terraces  in  Mountain 
Valleys  near  the  City  of  Mexico. 

1  =  Volcanic  tuff.  3  =  Pirst  alluvium. 

2  =  Caliche.  4  =  Second  alluvium. 

A,  B,  C  =  Successive  gorges. 

volcanic  deposits  suggests  a  long  dry  epoch;  the  rapid  cutting  to  form  the  gorge  A  indicates 
a  pronounced  uplift  or  else  a  period  of  comparative  moisture,  during  which  the  streams 
were  either  of  large  volume  or  else  were  not  overloaded  with  detritus  because  of  the 
covering  of  the  slopes  with  vegetation.  In  either  case  they  were  able  to  erode  rapidly. 
The  alluvial  filling,  3,  indicates  either  a  tilting  of  the  earth's  crust  back  towards  its  original 
position  or  a  period  of  aridity  which  would  cause  deposition  either  by  diminishing  the 
streams,  or,  more  likely,  by  increasing  their  load  through  the  death  of  vegetation  and 
consequent  releasing  of  the  soil.  The  process  of  cutting  and  filling  was  repeated  at  least 
twice,  and  may  have  been  repeated  several  times,  although  the  evidence  is  now  concealed 
or  has  been  worn  away. 

Similar  phenomena  on  a  much  larger  scale  occur  farther  south,  especially  in  the  valley 
of  the  Papaloapam  River,  nearly  200  miles  southwest  of  Mexico  City,  between  Puebla  and 
Oaxaca.  Here  the  terraces  reach  a  height  of  at  least  200  to  300  feet,  and  are  developed 
to  the  number  of  four  over  long  distances.  Still  farther  south,  in  Guatemala,  only  15°  from 
the  equator,  terraces  are  found  in  an  equally  well-developed  condition,  as  will  be  described 
later.  They  are  of  the  same  type  as  those  in  regions  hundreds  and  thousands  of  miles 
away,  and  appear  to  be  due  to  a  common  cause  which  can  scarcely  be  anything  but  chmatic 
pulsations.  The  constant  occurrence  of  such  terraces  from  Utah  on  the  north  through 
Mexico  to  the  far  south,  and  their  high  development  even  at  the  southern  limit  to  which  they 
have  yet  been  traced,  seem  to  be  strong  indications  that  climatic  changes  have  taken  place 
in  Mexico  as  well  as  in  the  United  States.  The  lakes  of  Mexico  and  the  traces  of  ancient 
cultures  in  the  strata  forming  the  floor  of  the  Mexican  basin  suggest  that  here,  as  elsewhere, 
the  later  changes  have  taken  place  since  man  reached  a  stage  of  comparative  civilization. 


CHAPTER  XI. 


A  METHOD  OF  ESTIMATING  RAINFALL  BY  THE  GROWTH  OF 

TREES. 


By  a.  E.  Douglass,  Sc.D.,  of  the  University  of  Arizona. 


In  the  great  northern  plateau  of  Arizona,  lying  at  an  average  altitude  of  6,000  feet  above 
the  sea,  the  higher  elevations  are  covered  with  forests  of  yellow  pine  (Pinus  ponderosa), 
a  fine  timber  tree  with  a  heavy  cyhndrical  trunk  and  rather  bushy  top.  The  trees  are 
scattered  gracefully  over  the  plains  and  hills  and,  with  the  remarkable  absence  of  under¬ 
growth,  render  travel  through  their  shady  midst  attractive  and  dehghtful.  For  centuries 
these  magnificent  pines  have  stood  there,  endming  the  vicissitudes  of  heat  and  cold,  flood 
and  drought.  They  have  not  been  subjected  to  a  mild  climate  for,  contrary  to  common 
opinion,  northern  Arizona  has  really  a  cold  climate.  Several  feet  of  snow  lie  on  the  ground 
during  the  winter,  and  the  summer  days,  though  hot  in  the  sun,  are  cold  in  the  shade. 
Hence  the  growth  of  the  trees  is  sharply  limited  to  the  warmer  season.  The  chmate  of 
Arizona  presents  not  only  a  strong  contrast  between  summer  and  winter,  but  between 
successive  years,  the  rainfall  in  some  years  being  no  more  than  a  quarter  as  much  as  in 
others.  This  being  the  case,  it  would  seem  that  the  trees  must  contain  some  record  of  the 
climatic  variations  through  which  they  have  lived.  Other  methods  of  studjdng  this  matter 
enable  us  to  go  back  only  from  twenty  to  sixty  years  to  the  beginning  of  meteorological 
records  in  Arizona.  The  trees,  however,  if  they  prove  to  convey  any  information  at  all, 
will  yield  data  covering  two  to  five  centuries. 

The  possibihty  that  the  trees  might  serve  as  indices  of  the  climate  of  the  past  led  the 
author  to  begin  investigation  of  the  matter  in  1901.  His  line  of  reasoning  was  as  follows: 

(1)  The  rings  of  a  tree  measure  its  food  supply. 

(2)  Food  supply  depends  largely  upon  the  amount  of  moisture,  especially  where  the 
quantity  of  moisture  is  limited  and  the  life  struggle  of  the  tree  is  against  drought  rather 
than  against  competing  vegetation. 

(3)  In  such  countries,  therefore,  the  rings  are  likely  to  form  a  measure  of  the  precipi¬ 
tation. 

In  planning  the  work  three  fundamental  steps  were  anticipated.  First,  to  prepare  a 
curve  of  tree  growth;  second,  to  find  if  there  exists  in  this  any  connection  with  precipitation; 
third,  by  carrying  this  back  through  long  periods  to  find  whether  meteorological  variations, 
if  discovered,  show  association  with  astronomical  phenomena. 

Note. — Throughout  the  present  investigation  our  purpose  has  been  to  employ  as  many  different  methods  as 
possible  and  to  apply  them  in  as  many  places  as  possible.  _  Our  danger  has  been  that  the  framer  of  a  theory,  having 
developed  new  lines  of  reasoning,  is  apt  to  become  so  convinced  of  their  validity  that  he  sees  everything  from  a  biased 
standpoint.  Fortunately,  however,  we  are  able  to  neutralize  this  danger  by  means  of  a  new  method  of  investigation, 
a  method  entirely  independent  of  those  hitherto  discussed,  and  one  so  exact  in  character  that  the  personal  opinion 
of  the  investigator  has  little  influence  upon  the  main  results.  This  method  was  suggested  by  Professor  A.  E.  Douglass, 
of  the  University  of  Arizona,  in  an  article  published  in  the  Monthly  Weather  Review  for  June  1909,  under  the  title 
“Weather  Cycles  in  the  Growth  of  Big  Trees.”  It  does  not,  to  be  sure,  shed  light  on  the  problem  of  the  influence 
of  climatic  changes  upon  human  actions  and  history,  but  it  enables  us,  by  means  of  actual  measurements,  to  a^er- 
tain  exactly  what  kinds  of  changes  have  taken  place  and  at  exactly  what  dates.  _  The  final  determination  of  these 
things  is,  of  course,  a  long  process,  and  can  not  be  completed  for  many  years,  but  important  results  can  be  obtained 
at  once.  In  order  that  the  reader  may  have  a  first-hand  statement  of  the  matter,  I  have  asked  Professor  Douglass 
to  contribute  to  this  volume  a  chapter  which  shall  embody  not  only  his  original  work  as  described  in  1909,^but  certam 
measurements  which  he  has  since  made,  and  upon  which  he  bases  fuller  conclusions.  Professor  Douglass  s  contribu¬ 
tion  is  inserted  without  further  comment. — E.  H. 


101 


102 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


ADVANTAGES  OF  LOCATION. 

The  pine  tree  of  northern  Arizona  lends  itseK  peculiarly  well  to  the  investigation  here 
contemplated.  Not  only  is  its  situation  favorable  because  of  the  absence  of  other  vege¬ 
tation  and  of  all  pests  which  might  seriously  alter  the  growth  of  the  tree,  but  because  the 
soil  is  of  such  a  nature  that  variations  in  precipitation  are  quickly  felt  in  the  trees.  Of 
still  more  importance  is  the  fact  that  the  relatively  open  and  unobstructed  character  of 
the  country  makes  the  meteorological  elements  relatively  homogeneous  over  a  consider¬ 
able  area,  and  tree  records  from  widely  separated  localities  show  similar  features.  The 
importance  of  this  is  illustrated  by  the  conditions  near  Flagstaff.  To  the  south  of  the 
town,  where  the  tree  records  were  obtained,  the  altitude  averages  about  7,000  feet,  and  varies 
only  a  few  hundred  feet  from  place  to  place.  North  of  the  town,  however,  the  San  Fran¬ 
cisco  Peaks  rise  about  12,700  feet,  and  the  yellow  pine  extends  up  their  slopes  to  about 
9,000  feet.  On  the  side  of  the  mountain,  exposed  to  the  prevalent  westerly  storms,  the 
snowfall  is  heavy.  There  are  found  all  the  springs  and  ranches,  and  the  overland  stage 
line  to  the  Grand  Canyon  goes  that  way  in  spite  of  heavy  grades,  for  there  water  can  be 
obtained  for  the  horses.  On  the  east  side  there  is  little  snow,  barren  park  lands  abound, 
and  the  traveler  has  a  run  of  25  miles  between  watering-places.  This  represents  the 
disadvantage  of  the  very  mountainous  region,  for  different  sides  of  a  high  range  present 
different  meteorological  conditions. 

Southeast  of  Flagstaff  the  plateau  country  extends  nearly  100  miles  to  the  so-called 
rim,  where  the  land  drops  off  to  the  lower  levels  of  southern  Arizona,  while  to  the  south¬ 
west  the  rim  is  50  miles  distant.  On  the  slopes  of  the  rim  the  trees  go  down  to  an  elevation 
of  about  5,500  feet.  Here  the  trees  are  peculiarly  sensitive  to  changes  in  rainfall,  since 
they  live  under  severe  conditions  due  to  the  decrease  of  the  rainfall  with  decreasing  altitude. 
They  are  so  sensitive,  indeed,  that  in  extremely  dry  years  the  older  trees  sometimes  omit 
the  formation  of  any  ring  whatever.  Such  an  omission  is  of  course  significant,  but  it  is 
an  exaggeration  of  the  actual  conditions  and  it  leads  to  grave  errors.  Besides  the  trees  from 
near  Flagstaff,  others  were  collected  from  the  mountain  around  Prescott,  southwest  of 
the  rim  across  the  deep  Verde  Valley.  Among  the  high  and  broken  ridges  of  that  region 
the  rainfall  on  opposite  sides  of  a  ridge  may  vary  greatly.  Hence  nearly  60  trees  from 
various  localities  were  measured  before  a  growth  was  found  close  enough  to  Prescott  to 
be  compared  minutely  with  records  of  precipitation  at  that  place. 

SEASONAL  CONDITIONS  AND  TREE  GROWTH. 

The  climate  of  this  part  of  Arizona  possesses  the  general  characteristics  described  in  an 
earlier  chapter  of  this  book.  Because  of  the  altitude,  the  winter  temperature  often  falls 
from  15°  to  20°  F.  below  zero.  Shallow  valleys  are  especially  subject  to  low  temperatures, 
for  in  the  absence  of  general  or  storm  winds,  such  as  prevail  over  the  eastern  part  of  the 
country,  the  cold  air  settles  in  the  lowest  places.  Even  in  summer  the  temperature  is 
often  low  and  snowstorms  not  infrequently  occur  in  May,  and  during  the  last  18  years 
one  occurred  in  June.  These  conditions  favor  very  perfect  ring  production,  but  the  divi¬ 
sion  of  the  rainfall  into  a  winter  and  summer  season  is  a  disadvantage  in  the  attempt  to 
investigate  climate  by  means  of  the  growth  of  trees,  for  the  spring  drought  naturally  checks 
growth  and  some  of  the  trees  often  act  as  if  winter  were  approaching,  and  form  a  layer  of 
hard  wood  like  that  characteristic  of  the  fall.  Usually  such  trees  begin  to  grow  again  when 
the  summer  rains  come,  and  thus  form  a  double  ring,  but  some  stop  growing  entirely. 

Meteorological  records  in  northern  Arizona  are  necessarily  meager,  yet  not  so  deficient 
as  might  be  expected.  The  country  was  first  settled  in  the  fifties,  when  gold  was  dis¬ 
covered  in  Arizona  as  well  as  in  California,  and  lines  of  travel  were  established  from  Santa 
Fe  westward  across  the  plateau.  The  “blazings”  on  the  pine  trees  marking  the  earlier 
roads  are  still  to  be  distinguished.  Soon  after  the  opening  of  the  country  the  government 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


103 


located  military  camps  at  various  places,  and  from  that  time  records  of  rainfall  and  tem¬ 
perature  were  kept.  The  record  at  Whipple  Barracks,  near  Prescott,  which  was  begun  in 
1867,  has  been  continued  to  the  present  time.  It  is  the  longest  consecutive  record  in  the 
pine  forest,  and  is  therefore  made  use  of  below.  Aside  from  rainfall,  other  meteorological 
elements,  especially  temperature,  must  have  an  effect  upon  tree-growth,  but  I  have  not 
attempted  to  include  them  in  this  work,  for  it  seemed  desirable  to  ascertain  the  degree  of 
relationship  of  the  growth  of  trees  to  one  single  element  before  going  on  to  others. 
Moreover,  it  is  probable  that  the  various  climatic  elements  have  so  distinct  a  relation  to 
each  other  that  the  investigation  of  one  will  throw  light  on  the  rest. 

The  plateau  and  the  chmate  are  not  the  only  features  of  northern  Arizona  which  favor 
an  investigation  of  the  sort  here  contemplated.  The  yellow  pine  itself  is  favorable,  because 
of  its  conspicuous  annual  rings.  The  differences  between  the  soft,  rapidly  growing  white 
tissues  of  the  spring  and  summer  and  the  hard,  reddish  layers  formed  in  the  fall  are  much 
less  conspicuous  in  most  of  the  common  trees  than  in  the  pine.  The  sharp,  outer  edge  where 
the  growth  of  the  hard,  red  layer  is  checked  by  the  cold  of  winter  gives  a  precise  point 
from  which  to  measure.  The  chief  growth  of  the  tree  consists  of  a  wide,  white,  pulpy, 
summer  ring,  whose  cells  are  round  and  well-shaped.  As  conditions  of  growth  become 
less  favorable,  the  cells  become  lean  and  emaciated  and  take  on  a  red  color.  The  autumn 
ring  thus  formed  is  thin,  hard,  and  pitchy.  On  the  inner  side  it  merges  gradually  into 
the  summer  ring,  but  on  the  other  side  it  is  sharply  limited  by  the  spring  growth  of  the 
next  year.  Where  a  double  ring  is  formed,  the  white  portion  of  the  secondary  ring  is 
usually  narrow  and  poorly  developed. 

THE  COLLECTION  AND  MEASUREMENT  OF  SECTIONS. 

At  the  beginning  of  the  investigation  it  was  foreseen  that  enough  trees  would  have  to 
be  measured  to  give  a  real  average.  The  trees  would  have  to  spread  over  enough  country 
and  be  sufficiently  numerous  to  ehminate  accidents  of  grouping  and  other  minutely  local 
conditions,  and  yet  they  must  not  extend  into  other  meteorological  regions;  they  must  be 
numerous  enough  to  be  susceptible  of  division  into  groups,  which  show  common  char¬ 
acteristics  and  thus  testify  to  the  genuineness  of  whatever  variations  appeared.  Work 
was  begun  in  January  1904,  when  I  visited  the  log  yards  of  The  Arizona  Lumber  and 
Timber  Company,  Flagstaff,  and  spent  several  hours  in  the  snow,  measuring  the  rings  of 
section  No.  1.  For  subsequent  measurements  Mr.  T.  A.  Riordan,  president  of  the  company, 
most  kindly  came  to  my  assistance  by  having  thin  sections  cut  from  the  ends  of  logs  or 
stumps  and  sent  to  me  in  town,  there  to  be  measured  more  conveniently.  Sections  VII 
to  XXV  were  cut  at  my  direction  on  the  spot  where  the  trees  grew,  and  where  I  was  able 
to  mark  the  points  of  the  compass  on  the  sections  and  otherwise  identify  and  describe 
their  location.  These  19  sections  were  freighted  to  Tucson,  where  the  work  on  them  was 
done.  The  method  of  measurement  consists  in  determining  the  radial  thickness  of  each 
annual  ring  m  millimeters.  The  average  age  of  the  trees  was  348  years.  The  total  number 
of  individual  measurements  reached  over  10,000. 

In  the  first  comparisons  between  tree  growth  and  rainfall  the  measures  from  six  sections 
only  were  used  and  comparison  was  made  with  the  Prescott  weather  records,  for  the  Flag¬ 
staff  station  had  been  in  existence  only  6  years.  At  that  time  there  was  no  thought  of 
any  such  remarkable  relation  between  yearly  growth  and  yearly  rainfall  as  has  since  been 
found;  therefore,  such  relationship  was  not  even  tested  until  later.  For  purposes  of  com¬ 
parison,  smoothed  curves  were  used,  “the  nine-year  smoothed”  being  the  one  chiefly  em¬ 
ployed.  Inasmuch  as  we  were  then  attempting  to  study  the  general  condition  of  the  country 
rather  than  the  individual  year,  and  as  the  influence  of  good  or  bad  conditions  of  rainfall 
lasts  some  years,  the  average  of  the  eight  preceding  years  and  of  the  year  in  question  was 
plotted  in  place  of  the  rainfall  of  any  single  year.  From  such  smoothed  curves  a  connection 


104 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


between  the  precipitation  at  Prescott  and  the  annual  tree-growth  nearly  70  miles  distant 
seemed  evident.  Later  studies  have  confirmed  this  conclusion  and  show  that  the  agree¬ 
ment  between  tree-growth  and  rainfall  is  fairly  close  when  the  two  are  measured  at  approxi¬ 
mately  the  same  place.  For  more  distant  localities  an  agreement  in  individual  years  is 
not  to  be  expected,  but  averages  of  three  or  more  years  show  strong  similarity,  even  in 
places  so  far  apart  as  Prescott  and  the  Californian  Coast,  500  miles  to  the  west.  As  soon 
as  it  became  evident  that  the  method  under  consideration  gave  genuine  results  further 
measurements  were  made.  Lists  of  the  sizes  of  individual  rings  of  each  of  25  trees  w^ere 
prepared.  The  trees  were  divided  into  three  groups  consisting  of :  A,  6  trees  from  3  miles 
south  of  Flagstaff;  B,  9  trees  from  about  11  miles  southwest  of  Flagstaff;  C,  10  trees  a 
mile  west  of  the  last  group.  A  comparison  of  the  three  groups  clearly  reveals  the  general 
character  of  the  longer  periodicities  hereafter  to  be  discussed  and  shows  many  lesser 
variations  common  to  the  three  groups.  Interesting  differences  also  appear  corresponding 
to  the  location  in  which  the  trees  grew.  Group  A  dropped  to  strong  minima  in  1780 
and  1880  more  promptly  than  the  others.  This  appears  to  be  due  to  the  fact  that  it  grew  in 
a  porous  hmestone  soil  lying  upon  rocks  full  of  crevices.  The  other  groups  grew  on  recent 
lavas,  very  compact  and  unbroken  and  covered  with  rather  a  thin  layer  of  clayey  soil. 
In  the  region  where  group  A  grew,  the  rain  passed  quicldy  through  the  soil  and  was  not 
so  well  conserved  as  in  the  other  groups  where  the  water  could  find  no  convenient  outlet. 

Other  interesting  facts  came  to  light.  It  was  especially  noticeable  that  a  given  year  of 
marked  peculiarities  could  be  identified  in  different  trees  with  surprising  ease.  For  instance, 
this  is  illustrated  in  Plate  4,  w^here  shavings  from  three  of  the  Flagstaff  trees  have  been 
photographed,  and  the  photographs  have  been  enlarged  to  such  a  scale  that  the  distance 
from  the  ring  for  1898,  indicated  by  the  upper  line  of  black  crosses,  to  1851,  the  lower  line 
of  crosses,  is  equal  in  all  cases.  The  other  lines  of  crosses  indicate  the  noticeably  broad  rings 
of  1868  and  1878.  An  examination  of  the  photographs  shows  that  the  most  characteristic 
feature  is  a  group  of  narrow  rings  about  the  years  1879  to  1884.  These  can  be  identified  in 
practically  every  tree,  and  an  examination  of  stumps,  which  were  not  measured,  showed 
that  it  was  easy  to  pick  them  out  wherever  one  chose.  Striking  verification  of  this  was 
found  in  the  case  of  a  stump  near  town  which  had  been  cut  about  20  years  previously. 
By  finding  this  group  of  rings  the  writer  was  able  to  name  the  year  when  the  tree  was  felled 
and  the  date  was  verified  by  the  owner  of  the  land.  In  the  more  recent  work  this  same 
group  shows  conspicuously  among  Prescott  trees,  and  in  general  95  per  cent  of  these 
trees  have  rings  so  characteristically  marked  that  the  identification  of  the  same  series  of 
rings  can  be  made  with  little  doubt,  whether  at  Flagstaff  or  at  Prescott. 

As  a  rule,  the  thickness  of  a  given  ring  is  not  uniform  on  all  sides  of  the  tree.  It  varies 
for  accidental  reasons,  and  also  according  to  the  points  of  the  compass.  In  the  19  trees 
of  groups  B  and  C  the  maximum  growth  occurs  a  little  to  the  east  of  north.  The  average 
variation  between  the  maximum  growth  in  the  northerly  direction  and  minimum  growth 
to  the  south  is  12  per  cent.  The  explanation  of  the  increased  growth  to  the  north  is  in  the 
increased  amount  of  moisture  on  that  side,  due  to  the  slower  melting  of  snow  and  the 
decreased  evaporation  in  the  shade.  For  nearly  all  these  trees,  also,  the  ground  had  a 
gentle  slope  toward  the  south,  so  that  moisture  working  downhill  would  come  to  the  north 
side  first.  All  of  these  facts  agree  in  pointing  to  moisture  as  the  factor  of  greatest  influence 
in  tree  growth. 

THE  DATING  OF  RINGS. 

In  comparing  the  growth  of  trees  and  the  rainfall  over  long  periods  of  years,  it  is  essen¬ 
tial  that  the  date  of  formation  of  any  individual  ring  shall  be  certain.  There  is  little 
danger  that  two  rings  will  coalesce,  for  the  cold  winters  at  an  elevation  of  7,000  feet  cause 
the  seasonal  growth  to  be  sharply  defined.  The  mean  temperature  of  29°  F.  in  January 
is  so  different  from  that  of  65°  F.  in  July  that  the  ring  of  one  year  is  nearly  always  clearly 


HUNTINGTON 


PLATE  4 


1898 


1878 


1868 


1851 


THE  CROSS  IDENTIFICATION  OF  RINGS  OF  GROWTH 


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METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES.  105 

separated  from  that  of  the  next.  Nevertheless,  the  rings  may  be  so  thin  that  they  can 
not  easily  be  distinguished,  and  seem  to  merge  into  one,  but  a  microscopic  examination 
usually  shows  indications  of  a  soft,  white  ring  as  well  as  of  a  hard,  red  ring  for  each  year. 
As  a  rule,  therefore,  each  annual  ring  is  extremely  well  marked,  and  there  is  no  doubt 
as  to  its  purely  annual  or  seasonal  character.  In  some  few  cases,  however,  rings  die  out 
completely,  while  in  others  they  are  double.  In  the  first  investigation  of  the  trees  at  Flag¬ 
staff,  it  was  estimated  that  the  results  were  subject  to  an  error  of  2  per  cent,  most  of 
which  occurred  near  the  center  of  the  tree.  The  more  rigorous  methods  subsequently 
employed,  however,  proved  that  the  error  of  unchecked  counting  in  these  trees  was  4  per 
cent  and  lay  almost  entirely  in  the  recent  years.  It  was  due  chiefly  to  the  omission  of 
rings  or  the  merging  of  several  together,  apparently  from  lack  of  nutrition.  The  number 
of  trees  in  which  serious  errors  are  found  is  not  sufficient  to  prevent  the  curves  of  growth 
and  of  rainfall  from  showing  close  agreement.  Mistakes  can  be  guarded  against  only  by 
a  process  of  cross-identification  which  will  be  described  shortly.  The  effect  of  the  unde¬ 
tected  omission  or  the  doubling  of  rings  in  individual  trees  is  to  lessen  the  intensity  of  the 
variations  in  the  curve  of  growth  obtained  by  the  averaging  of  many  trees.  The  errors 
may  be  divided  into  two  classes;  first,  local  errors  of  identity  in  small  groups  of  rings  in 
a  few  individual  trees,  which  simply  flatten  the  curve  without  affecting  the  final  count; 
second,  cases  in  which  a  given  ring,  in  spite  of  attempts  at  cross-identification,  is  still  in 
doubt,  showing  perhaps  in  half  of  the  trees,  and  not  in  the  other  half.  Such  cases  affect 
the  final  count  but  do  not  flatten  the  curve.  One  case  of  this  sort  will  be  noted  below. 
It  leaves  a  question  of  one  year  in  the  dating  of  all  the  earlier  portions  of  the  curve. 

THE  TREES  OF  PRESCOTT. 

The  problem  of  cross-identification  is  well  illustrated  in  the  trees  of  Prescott.  These 
were  measured  in  1911  for  the  purpose  of  testing  the  conclusions  derived  from  the  Flagstaff 
trees  some  years  earlier.  Prescott  was  chosen  because,  as  has  already  been  said,  the 
weather  records  there  go  back  to  1867  with  only  slight  breaks.  From  that  date  until  1898 
the  observations  were  made  at  Fort  Whipple,  about  a  mile  northeast  of  the  town,  and  from 
1898  to  the  present  time  they  have  been  taken  on  the  southwest  edge  of  town.  The  small 
breaks  referred  to  were  chiefly  in  the  summer  of  1869.  These  have  been  supplied  approxi¬ 
mately  by  comparison  with  the  records  in  other  parts  of  Arizona  during  the  years  1866  to 
1870,  but  there  is  still  a  question  of  several  inches  for  the  total  July  and  August  rains  for 
1869.  The  cuttings  from  tree  stumps  in  the  Prescott  region  were  procured  through  the 
assistance  of  Mr.  C.  H.  Hinderer,  supervisor  of  the  Prescott  National  Forest.  The  region 
about  Prescott  has  been  in  the  Forest  Reserve  since  1898,  and  no  cutting  has  been  allowed 
except  by  special  permit,  but  by  the  records  he  was  able  to  tell  just  when  the  trees  had 
been  cut.  The  trees  used  were  all  of  average  size,  being  several  hundred  years  of  age; 
the  cuttings  were  made  from  the  edges  of  the  stumps  and  were  intended  to  include  the 
last  fifty  years  or  so.  Sixty-four  were  measured  and  the  data  in  regard  to  them  are 
shown  in  table  1. 


Table  1. — Trees  of  Arizona. 


Group. 

No.  of 
trees. 

Elevation. 

Distance  from 
Prescott. 

Exposure. 

Drainage. 

Date  of  cutting. 

1 

s 

6,125 

1911,  May  and  June. 

2 

24 

6,420 

8  miles  S. 

Westerly . 

Groom  Creek .... 

1909,  July  to  Sept. 

3 

12 

6,800 

10  miles  S. 

Northerly . 

Hassayampa  .... 

1910,  Oct.  to  Nov. 

4 

10 

6,420 

8  miles  S. 

Westerly . 

Groom  Creek .... 

1909,  July  to  Sept. 

5 

10 

5,400 

1  mile  S. 

Northeasterly. . . . 

Granite  Wash  .  ,  . 

1909,  Summer. 

Besides  the  cuttings  shown  in  table  1,  three  others  were  measured,  two  in  the  first  group 
and  one  in  the  third,  but  were  finally  omitted  because  their  oldest  rings  did  not  date  back 


106 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


to  1867,  when  the  rainfall  record  begins.  Two  others  in  the  first  group,  with  40  and 
41  rings,  respectively,  one  in  the  second  with  38  rings,  and  one  in  the  third  with  41,  were 
made  use  of,  although  they  did  not  quite  go  back  the  necessary  43  years.  The  values  of 
the  deficient  rings  were  supplied  by  extrapolation  and  comparison. 

Of  these  five  groups  the  first  fom  were  collected  in  the  autumn  of  1911,  measured,  and 
their  average  curves  drawn.  While  the  comparison  with  the  annual  rainfall  gave  very 
promising  results,  it  was  apparent  that  the  agreement  between  growth  and  precipitation 
increases  as  the  location  of  the  actual  rainfall  station  is  approached  This  sustained  the 
opinion  of  Mr.  R.  H.  Forbes,  Director  of  the  Agricultural  Experiment  Station  at  the 
University  of  Arizona,  that  rainfall  in  the  mountainous  region  about  Prescott  is  extremely 
variable,  and  for  individual  years  one  point  can  not  be  judged  safely  from  others.  This 
made  it  necessary  to  get  some  samples  from  nearer  town.  Mr.  Hinderer,  therefore,  went 
to  the  further  trouble  of  finding  some  stumps  which  were  near  town,  about  a  dozen  in  all, 
from  which  the  ten  sections  of  the  last  group  were  cut.  These  ten  show  so  much  greater 
agreement  with  the  rainfall  than  do  the  others  that  they  have  been  used  alone  in  the  final 
conclusions. 

The  chief  feature  of  the  Prescott  series  which  places  its  results  on  a  firmer  basis  than 
any  previous  work  is  the  cross-identification  of  rings  between  trees.  The  extent  and 
accuracy  of  this  identification  came  as  a  surprise  to  the  writer.  After  measuring  the  first 
18  sections  it  became  apparent  that  much  the  same  succession  of  rings  occurs  in  each, 
and  thereupon  the  other  sections  were  examined  and  the  appearance  of  some  60  or  70  rings 
memorized.  All  the  sections  were  then  reviewed,  and  pin-pricks  placed  in  the  wood 
against  certain  rings.  Certain  characteristics  were  noted  as  common  to  all,  for  example, 
the  red  ring  of  1896  is  nearly  always  double,  while  the  rings  of  1884  and  1885  are 
wider  than  their  neighbors.  The  most  conspicuous  feature  was  a  series  of  compressed 
rings  from  1878  to  1883,  preceded  by  a  very  faint  1877  and  then  a  long  series  of  very  wide 
rings. 

Out  of  67  sections  averaging  50  rings  each,  only  6  gave  any  trouble  at  the  start. 
In  two  of  these,  2  rings  were  lacking,  but  when  allowance  was  made  for  this  defect,  the 
identification  of  the  remainder  was  satisfactory.  Another  section  had  2  extra  rings,  and 
another  had  2  extra  and  3  lacking.  The  other  two  sections  proved  especially  puzzling. 
It  finally  appeared  fairly  certain  that  one  of  them  had  the  rings  from  1879  to  1887  merged 
into  one,  and  the  rings  from  1890  to  1895  merged  into  one.  The  other  had  the  rings  for 
1890  to  1895  in  one  and  1898  to  1900  in  one.  Of  these  six  troublesome  sections,  the  first 
five  were  very  slow  growers.  Hence  it  would  seem  advisable  not  to  use  extremely  slow- 
growing  trees  any  more  than  is  necessary.  In  objection  it  may  be  urged  that  the  trees 
do  not  grow  continuously  at  the  slow  or  fast  rate,  and  we  can  not  tell  how  much  of  the 
change  is  due  to  rainfall.  On  the  whole,  however,  it  seems  advisable  to  exclude  trees,  or 
parts  of  trees,  whose  identification  is  extremely  difficult.  The  inner  rings,  if  well  identi¬ 
fied,  may  be  extremely  useful  in  carrying  back  early  records,  as  the  slow-growing  trees  are 
likely  to  be  among  the  oldest. 

The  cross-identification  of  trees  from  the  Prescott  region  was  limited  to  an  area  only 
10  miles  long.  It  came  as  a  surprise,  then,  to  find  that  shavings  from  the  Flagstaff  sections, 
such  as  are  shown  in  Plate  4,  could  be  identified  at  once  in  terms  of  the  rings  at  Prescott. 
The  narrow  ring  of  1851  was  at  once  seen  to  correspond  to  one  in  the  Prescott  series.  The 
dense  series  from  1879  to  1883  likewise  had  its  counterpart  at  Prescott  and  formed  the 
portion  of  the  sections  which  gave  the  most  difficulties  in  identification.  On  the  whole,  so  far 
as  can  be  judged  without  minute  study,  the  Prescott  trees  from  relatively  high  elevations 
approximating  the  elevation  at  Flagstaff  have  a  considerably  closer  resemblance  to  the 
Flagstaff  section  than  do  those  from  trees  growing  at  lower  altitudes.  The  process  of 
cross-identification  appears  to  be  applicable  to  areas  far  removed  from  one  another.  Two 


METHOD  OF  ESTIMATING  KAINFALL  BY  GROWTH  OF  TREES. 


107 


trees  out  of  three  which  were  tested  from  the  Santa  Rita  Mountains  in  southeastern  Ari¬ 
zona,  200  miles  from  Prescott,  were  found  to  have  rings  which  could  readily  be  identified 
in  terms  of  the  Prescott  series. 


Fiq.  9. — Annual  Growth  of  Trees  at  Prescott,  Arizona. 

YEARLY  IDENTIFICATION. 

Let  us  now  return  to  the  application  of  the  process  of  cross-identification  to  the  trees  at 
Prescott.  Preliminary  to  the  enumeration  of  the  rings,  a  particularly  clean  section  was 
selected  and  its  rings  were  numbered  consecutively;  then  all  the  other  sections  were  com¬ 
pared  with  this  as  a  standard.  On  the  completion  of  67  sections  a  careful  review  was 
made,  and  only  three  cases  were  found  still  to  be  questionable.  At  that  time  the  following 
notes  were  made,  the  numbers  being  those  obtained  by  counting  back  from  the  outer  ring, 
that  is,  the  ring  of  1910 : 

“  No.  6  frequently  double,  mostly  single,  probably  really  1  year. 

Nos.  31  and  32,  mostly  1,  occasionally  clearly  2  years,  still  in  doubt. 

Nos.  53  and  54  occasionally  clearly  separate,  sometimes  very  close,  often  completely 
merged  in  one,  still  in  doubt.” 

Upon  further  examination  the  following  occurrences  were  noted:  No.  6  was  found 
double  or  triple  in  46  cases  and  single  in  21,  but  still  uncertain.  Nos.  31  and  32  were  found 


108 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


to  form  a  single  ring  in  22  sections,  a  double  ring  in  19,  and  to  be  clearly  separate  in 
only  11  cases.  They  seemed  to  represent  one  year.  Nos.  53  and  54  were  found  to  form 
a  single  ring  in  6  cases,  a  double  one  in  one,  and  clearly  2  in  the  remaining  24  cases  for 
which  sections  were  available ;  accordingly  they  were  considered  to  represent  two  years.  On 
comparing  the  plotted  curve  of  tree  growth  with  the  curve  of  rainfall,  the  two  were  found 
to  agree  more  closely  if  ring  No.  6  were  assumed  to  represent  two  years  (1903  and  1904) 
rather  than  one,  but  the  real  evidence  strangely  enough  came  from  Flagstaff.  The  cross¬ 
identification  between  the  sections  from  Prescott  and  Flagstaff  made  it  possible  to  identify, 
unquestionably,  most  of  the  rings,  both  before  and  after  1903,  and  Flagstaff  plainly  showed 
two  rings  in  place  of  the  doubtful  ring  or  rings  called  No.  6  at  Prescott.  Hence  this  was 
apportioned  to  the  two  years  1903  and  1904.  Apparently,  if  a  sufficient  number  of  com¬ 
parisons  be  made,  and  if  the  trees  thus  compared  be  distributed  over  widely  different 
localities,  the  yearly  identification  of  rings  may  be  made  with  almost  perfect  certainty. 

Year 


Fig.  10. — Annual  Rainfall  and  Growth  of  Trees  (Group  V)  at  Prescott. 
Dotted  line  =  BainfaU.  Solid  line  =  Growth. 


The  final  curves  resulting  from  the  process  described  above  are  given  in  figure  9. 
The  upper  four  curves  represent  the  amount  of  growth  year  by  year  of  each  of  the  four 
groups  mentioned  above.  The  lower  curve  shows  the  mean  of  all  four  groups.  It  will  be 
seen  that  on  the  whole  these  four  groups  from  different  localities,  10  miles  or  so  apart,  agree 
quite  closely.  Nevertheless,  as  has  already  been  said,  the  trees  of  the  group  nearest  to 
Prescott  agree  most  closely  with  the  rainfall  at  that  place.  Accordingly,  their  growth  has 
been  plotted  in  figure  10,  together  with  the  rainfall  at  Prescott.  On  the  whole  there  is 
much  agreement,  as  may  be  seen  by  comparing  the  crests  and  troughs  of  one  with  those 
of  the  other.  The  most  conspicuous  discrepancy  is  in  1886,  where  the  rainfall  decreases 
and  the  growth  of  the  trees  increases.  In  1873  the  growth  seems  to  have  responded  to 
the  decrease  in  rainfall,  but  to  a  greatly  diminished  degree.  The  tree  maximum  of  1875, 
one  year  behind  the  extreme  maximum  of  1874  in  the  rainfall,  is  entirely  reasonable,  since 
the  ground  may  become  so  saturated  that  the  effects  last  until  the  following  year.  The 
general  falling  off  of  the  tree  curve  during  the  last  twenty  years  will  be  discussed  later;  it 
is  due  merely  to  the  fact  that  the  trees  grow  slowly  in  old  age.  On  the  whole,  the  curves 
shown  in  both  figures  9  and  10  support  the  idea  not  only  of  the  similarity  of  the  rings  of 
a  given  year  in  different  trees,  but  of  a  proportional  relation  between  annual  rainfall  and 
annual  growth. 

The  conclusions  regarding  yearly  identity  drawn  from  the  curves  at  Prescott  are  sup¬ 
ported  by  those  of  Flagstaff.  In  addition  to  the  25  sections  procured  there  in  1904,  7 
others  were  procured  in  1911.  The  pieces  for  examination  were  not  cut  horizontally  as 
hitherto,  but  were  secured  by  making  two  slanting  saw-cuts  at  right  angles  to  one  another 
on  the  top  of  the  stump,  thus  bringing  away  a  triangular  pyramid  of  wood,  which  included 
the  outer  50  to  100  rings.  These  cuttings  were  for  the  purpose  of  checking  the  growth 
in  the  last  half  century  but  made  no  pretense  of  reaching  the  center  of  the  trees,  whose 
average  age  was  three  or  four  hundred  years.  Figure  11  shows  how  well  the  7  cuttings  of 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


109 


1911  agree  with  the  25  cuttings  of  1904-06.  The  7  came  from  about  12  miles  southeast 
of  the  town,  while  the  25  came  from  places  from  6  to  12  miles  farther  west.  The  general 
form  of  the  two  curves  is  strikingly  similar,  just  as  is  the  general  form  for  the  four  groups 
at  Prescott,  as  shown  in  figure  9.  This  similarity  indicates  that  even  a  small  group  of  trees, 
no  more  than  seven  in  number,  is  sufficient  to  give  results  of  considerable  accuracy.  Indeed, 
we  may  go  farther  and  say  that  a  single  tree  may  give  results  of  moderate  accuracy  pro¬ 
vided  it  grows  fast  enough,  and  provided  allowance  be  made  for  the  cumulative  effect  of 
a  series  of  good  or  bad  years  and  for  the  vagaries  due  to  the  age  or  special  position  of  the 


Year 

1870  1880  1890  1900  1910 


tree.  This  is  evident  in  figure  12,  where  the  7  sections  from  the  last  Flagstaff  group  are 
plotted  separately,  the  most  rapid  grower  at  the  top,  just  below  the  rainfall  curve,  and 
the  slowest  grower  at  the  bottom.  All  alike  rise  because  the  conditions  of  rainfall  in 
1900-10  were  more  favorable  than  in  1890-1900,  and  all,  but  especially  the  curve  of  sec¬ 
tion  4,  show  a  more  or  less  close  relation  to  the  curve  of  rainfall  at  Flagstaff,  even  though 
that  place  was  some  12  miles  away.  The  great  sinuosity  of  the  curve  of  section  4  as  com¬ 
pared  with  section  5,  at  the  bottom,  is  noteworthy,  for  section  4  was  cut  from  a  fast¬ 
growing  tree.  This  difference  supports  the  conclusion  already  reached,  that  slow-growing 
trees  are  of  less  value  than  rapidly  growing  ones  in  the  study  of  the  climate  of  the  past. 


no 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


MONTH  OF  BEGINNING  ANNUAL  MEANS. 

Before  passing  on  to  other  matters,  a  word  of  explanation  must  be  added  as  to  the 
method  of  calculating  the  rainfall.  That  it  must  take  some  time  for  the  transmutation 
of  rain  into  an  important  part  of  the  organic  tissue  is  evident.  It  has  often  been  asked  of 
the  writer  how  soon  the  rains  affect  the  trees.  There  is  evidence,  as  will  be  shown  later, 
that  the  summer  rains  often  have  an  almost  immediate  effect.  The  winter  precipitation, 
however,  is  more  remote  in  its  action.  Much  of  the  first  growth  in  the  spring  must  come 
from  precipitation  long  past,  and  a  large  part  of  the  yearly  growth  comes  from  the  melting 
of  the  fall  and  winter  snows.  It  seems  reasonable,  therefore,  to  consider  any  snowfall  as 
applying  to  the  following  yearly  ring. 

At  Flagstaff  the  precipitation  of  November  is  almost  always  in  the  form  of  snow,  and 
therefore  that  month  should  certainly  be  considered  as  falling  after  the  arboreal  new  year 
of  that  locahty.  In  view  of  the  uncertainty  as  to  the  exact  month  when  the  precipitation 
begins  to  have  an  influence  upon  the  growth  of  the  following  season,  and  in  view  of  prob¬ 
able  variations  in  different  years,  it  seemed  wise  to  test  the  matter  by  a  purely  empirical 
method.  The  annual  rainfall  was  ascertained  for  yearly  periods  beginning  (1)  with  July 
1  of  the  preceding  year,  (2)  with  August  1,  and  so  on  to  (9)  with  March  1  of  the  current 
year.  Another  method  involved  a  separating  of  the  summer  rains,  one-half  to  apply  on 
each  adjacent  winter,  while  a  final  method  involved  a  similar  division  of  the  winter  rains. 
This  was  done  for  12  years  at  Flagstaff  and  43  at  Prescott.  Part  of  the  Flagstaff  curves 
are  given  in  the  lower  part  of  figure  11,  where  the  rainfall  can  be  compared  with  the  growth 
of  the  trees.  The  11  curves  plotted  from  these  figures  were  found  to  have  substantial 
disagreements,  although,  of  course,  the  smoothed  curves  of  all  of  them  would  be  practically 
identical.  A  comparison  of  the  growth  of  the  tree  with  these  11  curves  showed  that  the 
use  of  the  year  beginning  November  1  at  Flagstaff  and  September  1  at  Prescott  gave  the 
closest  agreement  between  growth  and  rainfall.  At  Flagstaff  the  majority  of  the  trees 
came  from  a  thin  clay  derived  from  decomposed  lava,  and  so  there  was  little  depth  for  the 
storage  of  moisture.  At  Prescott  half  the  sections  of  group  5,  whose  curve,  it  will  be  remem¬ 
bered,  is  shown  in  figure  10,  came  from  trees  growing  in  a  porous  soil  of  decomposed  granite 
in  a  rather  flat  depression  with  retarded  drainage,  so  that  conservation  would  have  a  greater 
influence.  Perhaps  this  explains  why  the  year  beginning  September  1  gives  the  best  results 
there. 

THE  TIME  OF  YEAR  OF  RING  FORMATION. 

Among  the  problems  connected  with  the  relation  of  the  growth  of  trees  and  the  amount 
of  rainfall,  one  of  the  most  interesting  was  suggested  by  Mr.  R.  H.  Forbes,  of  the  Arizona 
Experiment  Station.  The  problem  is  to  determine  the  time  of  formation  of  the  red  or 
autumn  portion  of  the  rings,  and  the  causes  for  the  formation  of  double  rings.  Apparently 
the  red  cells  are  due  ultimately  to  a  decreasing  absorption  of  moisture  during  the  cold 
period  of  winter  when  the  ground  is  frozen.  This  study  is  the  more  necessary  because 
many  rings  in  the  Prescott  series  (although  very  few  in  the  Flagstaff  series)  show  a  faint, 
preliminary  red  ring  forming  a  double.  The  first  test  was  designed  to  determine  the 
character  of  the  rainfall  in  the  years  producing  such  double  rings.  The  half-dozen  most 
persistent  cases  were  selected,  and  in  each  of  these  the  red  ring  was  found  double  in  the 
following  number  of  cases:  4  out  of  10  in  1896;  5  out  of  10  in  1891;  7  out  of  10  in  1881; 
4  out  of  10  in  1878,  1872,  and  1871.  The  average  width  of  all  the  rings  was  1.55  mm. 
The  mean  rainfall  by  months  for  the  years  above  selected  was  found  and  is  plotted  in  the 
sohd  line  of  the  upper  diagram  of  figure  13.  Six  other  rings  showing  one  double  in  ten 
trees  in  1898,  but  no  doubles  in  1897,  1885,  1884,  1876,  and  1874,  and  averaging  1.54  mm. 
in  thickness,  were  then  selected  and  the  curve  of  rainfall  by  months  for  the  year  during 
which  they  grew  has  been  plotted  as  the  upper  dotted  line  in  figure  13.  The  curves  seem  to 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


Ill 


indicate  clearly  that  the  chief  cause  of  doubling  is  a  deficiency  of  snowfall  in  the  winter 
months,  December  to  March.  This  appears  to  mean  that  if  the  winter  precipitation  is 
sufficient  to  bridge  over  the  usual  spring  drought,  the  growth  continues  evenly  through 
the  year,  giving  a  large  single  ring  which  ends  only  in  the  usual  red  growth  as  the  severity 
of  winter  comes  on.  If,  however,  the  preceding  winter  precipitation  has  not  been  entirely 
adequate,  the  spring  drought  taxes  the  resources  of  the  tree  and  some  red  tissue  is  formed 
because  of  deficient  absorption  in  the  early  summer  before  the  rains  begin. 


Year 


Fig.  12. — Growth  of  Individual 
Trees  compared  with  Pre¬ 
cipitation  at  Flagstaff. 


Fig.  13 


Fig.  14 


Figs.  13  and  14. — Effect  of  Monthly  Distribution  of  Precipitation  on 
Thickness  of  Rings  of  Growth. 


It  appears  further  that  if  not  only  the  winter  snows  are  lacking,  but  the  spring  rains 
are  unusually  scanty,  then  the  tree  may  close  up  shop  for  the  year  and  produce  its  final 
red  tissue  in  midsummer,  gaining  no  immediate  benefit  from  the  summer  rains.  This 
appears  to  be  the  interpretation  of  the  lower  diagram  of  figure  13.  Here  the  same  6  big 
doubles  mentioned  above  are  plotted,  together  with  a  selected  list  of  6  small  singles  par¬ 
ticularly  deficient  in  red  tissues.  They  are  1904  (double  once  in  ten),  1902  (double  once 
in  ten),  1899  (single),  1895  (single),  1894  (single)  and  1880  (double  once  in  ten).  In  these 
it  is  evident  that  drought  in  the  spring  stops  the  growth  of  the  tree.  The  double  ring 
therefore  seems  to  be  an  intermediate  form  between  the  large,  normal,  single  ring,  growing 
through  the  year,  and  the  small,  deficient  ring,  ending  its  growth  by  midsummer.  This 
probably  explains  why  the  Prescott  trees  do  not  show  an  agreement  of  more  than  about 
70  per  cent  between  growth  and  rainfall.  It  suggests  also  that  the  Flagstaff  trees  which 
grow  under  the  conditions  of  more  rainfall,  and  which  have  very  few  double  rings,  give  a 
more  accurate  record  than  those  of  Prescott.  Consistent  with  this  view  of  the  doubling  is 
the  condition  of  the  outer  rings  in  the  various  Prescott  groups  collected  by  Mr.  Hinderer. 
These  trees  were  cut  during  various  months  from  May  to  November.  Naturally  those  cut 


Annual  precipitation  in  inches  (dotted  lines) 


112 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


in  May  are  in  the  midst  of  their  most  rapid  growth,  while  those  cut  in  sununer  may  or  may 
not  show  the  double  ring  just  forming.  The  conditions  are  shown  in  table  2. 


Table  2. 


Group. 

Date  of 
cutting. 

Season. 

Altitude. 

Remarks. 

1 

1911 

May,  June... 

6125 

9  out  of  10  show  white  tissue  only,  indicating  rapid  growth. 

2  and  4 

1909 

July  to  Sept.. . 

6420 

30  out  of  33  show  red  ring  just  forming;  this  is  probably  a 
doubling. 

5 

1909 

Summer . 

5800 

3  or  4  out  of  10  show  red  ring  just  forming;  probably  a 
double. 

3 

1910 

Oct.  and  Nov. 

6800 

All  12  show  white  without  red;  probably  a  large  single. 

By  reference  to  figure  14,  showing  the  curves  of  monthly  rainfall  for  1909  and  1910, 
it  will  be  seen  that  1910  would  be  likely  to  carry  its  growth  right  through  the  year  and 
produce  a  single  line,  as  in  group  3  above.  1909  is  of  intermediate  character,  having  heavy 
winter  precipitation  and  also  a  severe  spring  drought  of  3  months.  So  in  the  groups  cut 
at  this  time  33  out  of  43  show  a  red  ring  forming  in  July,  August,  or  September,  doubt¬ 
less  the  preliminary  ring  of  a  double.  This  lesser  red  ring  is  due  to  the  spring  drought. 


and  its  appearance  at  this  time  indicates  a  lag  of  a  couple  of  months,  more  or  less,  in  the 
response  of  the  tree  to  rain.  The  whole  matter  of  the  relative  thickness  of  the  red  and 
white  portions  of  the  rings  is  illustrated  in  figure  15.  The  heavy,  sinuous  line  shows  the 
rainfall  month  by  month  at  Prescott  throughout  the  43  years  under  consideration.  The  total 
rainfall  for  the  year  is  indicated  by  the  dotted  rectangles,  while  the  size  and  character  of 
the  rings  is  shown  in  the  solid  rectangles.  In  these  the  white  portion  indicates  white  tissue 
and  the  shaded  portion  indicates  red  tissue. 

MATHEMATICAL  RELATION  OF  RAINFALL  AND  GROWTH. 

All  the  preceding  investigations  lead  up  to  the  question  of  the  accuracy  with  which 
the  growth  of  trees  represents  the  rainfall.  The  final  answer  will  necessarily  require  a  large 
amount  of  work,  but  even  now  some  definite  idea  may  be  obtained.  In  order  to  answer 
this  question  an  effort  was  made  to  construct  a  mathematical  formula  for  calculating  the 
annual  growth  of  trees  when  the  rainfall  is  known.  Any  such  formula  must  perform  three 


J 


Monthly  Drecipitation  in  inchesfsolid  lines.) 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


113 


principal  functions:  first,  it  must  reduce  the  mean  rainfall  to  the  mean  tree  growth;  second, 
it  must  provide  a  correction  to  offset  the  increasing  age  of  the  tree;  and,  third,  it  must 
express  the  degree  of  conservation  by  which  the  rain  of  any  one  year  has  an  influence 
for  several  years.  In  a  formula  of  universal  apphcation,  other  factors  will  play  a  part, 
but  for  a  limited  group  of  trees  in  one  locality  they  can  be  neglected.  In  calculating  the 


1870  1880  1890  1900  1910 


c 


c 

.2 

.S' 

'G 

a 

0. 


Fig.  16. — Actual  Tree  Growth  Compared  with  Growth  Calculated  from  Rainfall. 
Fig.  17. — Five-year  Smoothed  Curves  of  Rainfall  and  Tree  Growth  at  Prescott. 


formula,  the  group  of  ten  trees  nearest  Prescott  was  used.  The  first  process,  namely,  the 
reduction  of  the  mean  rainfall  to  the  mean  tree  growth,  was  easily  accomplished.  Ex¬ 
pressed  in  actual  figures,  the  rainfall  was  about  250  times  the  average  thickness  of  the  rings. 
This  is  the  general  factor  K  in  the  formula  on  the  next  page. 

The  second  process,  namely,  the  correction  for  the  age  of  the  tree,  was  practically 
omitted  in  forming  the  curves  here  shown,  since,  judging  by  the  Flagstaff  curves,  its  effect 
would  be  very  slight  in  the  interval  under  discussion.  In  long  periods  it  is  an  immensely 
important  correction  and  its  effect  should  always  be  investigated.* 

The  third  process,  that  is,  the  calculation  of  the  effect  of  conservation,  is  far  more 
complicated  than  the  others  and  its  results  may  be  regarded  as  provisional  until  a  large 
number  of  further  investigations  have  been  made;  yet  already  very  promising  results  have 
been  obtained,  which  give  an  agreement  of  more  than  80  per  cent  between  the  calculated 
curve  and  the  curve  derived  from  actual  measurements,  as  is  shown  in  figure  16. 

There  are  two  features  of  the  conservation  factor  worth  calling  attention  to:  (1)  that 
in  this  dry  climate  it  appHes  better  as  a  coefficient  than  as  an  additive  term  (while  there  is 
evidence,  as  given  in  a  later  chapter,  that  the  additive  form  is  better  in  a  moist  climate), 
and  (2)  that  it  gives  a  prominent  place  to  “accumulated  moisture’’  as  commonly  used  in 
meteorology.  Accumulated  moisture  is  simply  the  algebraic  sum  of  the  amounts  by  which 


*  Over  short  periods  the  change  may  be  regarded  as  linear  and  a  convenient  formula  is  —  =1— fc(n  —  y), 

9y 


where  gn  =  growth  in  any  year  w,  =  growth  in  middle  year  of  series,  and  fc  =  a  constant,  which  was  0.0043  in  the 
Flagstaff  series;  in  this  form  it  may  be  used  in  the  general  formula. 

In  the  Flagstaff  curves  from  1700  to  1900  the  growth  proved  to  be  inversely  proportional  to  the  square  root  of 

10 

the  time  elapsed  since  the  year  1690,  and  is  closely  expressed  in  millimeters  by  the  formula:  Tn  =  ,  ■  ’ 

Vn  —  1d90 


Tn  is  here  the  tree  growth  for  the  year  under  discussion. 

If  G  be  the  mean  size  of  ring,  then  the  factor  to  be  introduced  in  a  general  formula  becomes 


10 

GVn-  1690 


9 


114 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


all  the  years  in  a  series  from  the  start  to  and  including  the  year  desired  depart  from  the 
mean.  It  may  be  expressed  by  a  formula,  thus 

■4„=  {Rn  —  M)-\-{Rn-\  —  M)-\-  •  •  •  {Ri  —  M)  =l?„  +  -Rn-l  +  jRn-2+  ‘  ’  *  Rl—uM 


and  conversely 

Rn  =  M-\-An  —  An-\ 

In  this  formula,  is  the  accumulated  moisture  for  the  nth  year  of  a  series  of  consecutive 
years  whose  mean  rainfall  is  M,  Rn  is  the  rainfall  for  that  nth  year,  and  Rn-i  is  the  rainfall 
of  the  next  preceding  year,  and  so  forth. 

Now  the  accumulated  moisture  curve  for  Prescott,  when  brought  to  proper  scale,  almost 
coincides  with  the  smoothed  curve  of  tree  growth:  hence  the  relation  of  the  smoothed 
curve  of  rain  (individual  years  vary  too  much)  to  the  accumulation  curve  represents  very 
successfully  the  temporary  relation  between  rainfall  and  tree  growth  and  it  is  only  neces¬ 
sary  to  change  the  annual  rain  in  the  same  proportion  to  produce  the  tree  growth,  as 
appears  in  figure  17.  The  smoothed  curve  of  rain  in  this  case  consisted  of  successive  or 
overlapping  5-year  means  used  in  the  place  of  the  middle  or  third  year.  For  example, 
the  average  rain  of  1881  to  1885  was  placed  in  1883,  the  average  of  1882  to  1886  was  placed 
in  1884,  and  so  forth.  Its  formula  appears  thus: 


—  5  (-R  n-2  + n-l  + -R  n  + -R  n+l  + -R  n+2) 


The  simple  empirical  formula  for  the  tree  growth,  T,  for  the  nth  year  of  this  series 
thus  was  found  to  be: 


Tn  =  K 


cM  dAn 


Rn 


in  which  c  and  d  are  small  constants  found  advantageous  in  reducing  the  accumulated 
moisture  curve  to  proper  scale.  In  actual  numbers  this  becomes 


T„  (in  inches) 


1 

2^ 


0.90M  4- 


•  (in  inches) 


The  mean  value  of  the  rainfall,  M,  is  17.1  inches. 


Fig.  18. — Actual  Rainfall  Compared  with  Rainfall  Calculated  from  Growth  of  Trees,  Arizona. 

- -  Observed  rain.  - -  Rain  calculated  from  trees. 


The  reversal  of  the  process  in  order  to  ascertain  rainfall  from  tree  growth  seems  to  be 
fulty  as  accurate  over  this  limited  period  and  its  result  is  shown  in  figure  18,  where  the  curve 
has  an  average  accuracy  of  82  per  cent  for  individual  years.  In  producing  this  reversal 
the  following  operations  were  performed : 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


115 


1 .  A  5-year  smoothed  curve  was  made  of  the  tree  growth  (expressed  in  millimeters) . 


This  gives  us  the  term 


3.6M  -1-  A 
250  •  4 


-  in  the  reversed  formula  Rn  = 


Sn 

S.OM  +  An 
250-4 


•T 


n 


2. 

3. 

4. 

5. 


This  term  is  multiplied  by  1,000,  reduced  to  inches,  and  3.6M  subtracted, 
leaving  in  inches. 

From  An,  an  approximate  Rn  is  found  by  the  formula  Rn  =  M  +  A„  —  A n-i 
This  series  of  approximate  rainfall,  Rn,  is  smoothed  and  becomes  the  Sn  of  the 
formula. 


Final  values  are  then  found  by  the  proportion: 


3.6ilf  -{-An 
250  -  4 


Sn'.’.Tn  :Rn 


It  should  be  emphasized  that  the  above  formula  for  conservation  is  the  one  found  to 
apply  under  dry  climatic  conditions.  In  moist  climates  the  trees,  so  far  as  observed,  seem 
to  depend  on  other  meteorological  elements  or  combination  of  elements. 

The  Prescott  trees,  as  we  have  seen,  even  without  correction,  give  a  record  of  rain¬ 
fall  with  an  accuracy  of  about  70  per  cent.  It  is  likely  that  the  Flagstaff  trees,  with  their 
higher  elevation,  more  certain  rainfall,  and  more  central  location  in  the  zone  occupied  by 
this  species,  give  somewhat  more  accurate  records.  They  are  probably  much  less  often 
subjected  to  extremes  of  dryness  which  throw  the  tree  out  of  its  equilibrium,  and  cause  it 
to  produce  an  abnormally  small  set  of  rings.  It  seems  likely,  also,  that  the  less  porous  and 
less  conservative  soil,  combined  with  a  more  abundant  precipitation,  produces  a  yearly 
growth  more  nearly  proportional  to  the  rainfall  than  at  Prescott. 


THE  FLAGSTAFF  SOO-YEAR  CURVES. 

Previously  in  this  chapter,  we  have  endeavored  to  determine  the  exact  relation  between 
growth  and  rainfall  and  to  ascertain  the  most  accurate  method  of  obtaining  results.  We 
shall  now  apply  these  conclusions  and  methods  to  the  oldest  available  trees.  For  this 
purpose  19  of  the  Flagstaff  sections  were  selected  and  were  subjected  to  minute  examination 
and  cross  identification,  in  order,  so  far  as  possible,  to  eliminate  all  errors  due  to  the  omission 
or  doubhng  of  rings.  For  convenience  in  handling  the  sections,  each  one  was  reduced  to 
a  strip  of  wood  extending  from  center  to  bark.  The  best  of  these  was  adopted  as  a  standard. 
It  was  then  compared  with  each  of  the  others,  ring  for  ring,  for  300  years.  In  this  long 
period  only  9  years  required  a  second  examination,  and  only  one  required  a  third.  This 
was  the  ring  for  1821,  which  was  often  merged  with  that  for  1822.  The  2  rings  appear 
as  one  in  10  sections  and  as  2  in  only  9  sections,  but  in  many  or  most  of  the  cases  where 
2  appear,  they  were  so  distinctly  separate  that  they  were  counted  as  representing  2  years. 
This  is  not  aboslutely  certain,  however,  and  thus  there  may  be  an  error  of  one  year  in 
the  portions  of  the  curve  of  growth  before  1821.*  So  far  as  is  known,  there  is  no  probability 
of  any  other  error.  In  order  to  show  the  value  of  cross-identifying  the  rings  of  one  tree 
with  those  of  another,  Table  J  has  been  inserted  on  page  330  of  this  volume.  It 
shows  the  errors  of  identification  in  the  original  measurements  of  1906,  when  the  same  sec¬ 
tions  were  reviewed  in  the  light  of  later  knowledge.  The  table  shows  the  exact  errors 
made  in  the  original,  straight-away  counting,  both  in  the  number  and  place  of  the  rings. 
It  is  pubfished  here,  partly,  because  it  corrects  the  various  errors  in  the  sections  of  corre¬ 
sponding  number  as  they  appear  in  the  Monthly  Weather  Review  for  June  1909. 

In  studies  like  the  present,  it  is  manifestly  desirable  to  carry  the  curves  of  growth  as 
far  back  as  possible.  Only  a  few  trees  go  back  to  an  age  of  over  300  or  400  years,  but 

*  Subsequent  comparison  with  historical  records  supports  the  identification  here  adopted.  The  data,  however,  were 

not  obtained  in  time  to  be  incorporated  in  this  volume. 


116 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


these  are  enough  to  give  approximately  correct  results,  although  greater  accuracy  is  of 
course  highly  desirable.  In  order  to  test  the  degree  of  accuracy  to  be  obtained  from  a 
small  number  of  trees,  a  comparison  was  made  between  large  groups  and  small.  After  the 
entire  group  of  rings  in  each  section,  some  6,300  in  all,  had  been  identified  and  numbered, 
the  sections  were  tabulated  in  order  of  age,  with  the  oldest  first.  They  were  then  separated 
into  groups  of  five,  and  in  a  convenient  manner  averages  were  obtained  of  the  oldest  five, 
going  back  about  400  years;  the  oldest  ten,  350  years;  the  oldest  fifteen,  300  years, 
and  the  entire  nineteen  reaching  back  only  200  years.  Finally,  at  the  ancient  end  of  the 
oldest  five,  the  oldest  two  were  carried  back  to  fully  500  years.  On  plotting  the  groups 


of  fifteen,  ten,  and  five  with  its  extension  of  two,  it  became  immediately  evident  that  five 
trees  gave  almost  the  same  growth  as  fifteen,  even  to  small  details.  So  in  the  work  dis¬ 
cussed  below,  the  five  are  used  to  give  the  record  from  1503  to  1908;  so  also  for  the  same 
reason  a  comparison  was  made  between  these  five,  and  the  two  oldest  taken  by  themselves. 
In  this  the  agreement  was  not  quite  so  perfect,  yet  was  so  close  that  errors  thus  introduced 
will  not  at  all  affect  the  curves  referred  to  below.  However,  the  two  oldest  were  very 
slow  growers,  and  5  mm.  were  added  to  all  their  records  where  only  these  two  were  used, 
in  order  to  make  their  curve  continuous  with  that  of  the  whole  five.  Thus  the  tree  record 
is  made  to  extend  from  1411  to  1908,  as  is  shown  in  figure  19.  Unfortunately,  it  must  not 
be  taken  for  granted  that  this  remarkable  agreement  between  very  small  groups  of  trees 
is  true  necessarily  for  other  trees,  or  even  for  this  yellow  pine  tree  under  all  conditions. 
It  is  without  doubt  due  to  the  fact  that  this  tree  under  semi-arid  conditions  is  extremely 
sensitive  to  varying  moisture  supply. 

This  extreme  sensitiveness  causes  one  fault  in  the  record,  namely,  the  frequent  omission 
of  rings  between  1891  and  1896,  as  is  evident  in  the  list  already  given;  the  complete  omission 
of  a  ring  is  an  exaggeration  which  should  be  guarded  against.  Accordingly,  these  years 
were  specially  investigated  in  both  rapid-growing  and  slow-growing  trees,  and  a  series  of 
growth  values  estimated  from  the  trees  which  did  not  omit  the  rings.  These  interpolated 
values  have  been  used  in  the  figure. 

As  has  already  been  said,  a  correction  is  needed  to  offset  the  faster  growth  of  trees  in 
youth  than  in  old  age.  This  has  been  made  empirically  by  drawing  a  long,  nearly  straight 
line  throughout  the  plotted  curve  for  500  years.  The  slope  in  this  line  shows  very  closely 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


117 


the  change  in  growth  with  advancing  age.  Long,  slow  variations  in  the  rate  of  growth 
may  not  cause  any  divergence  from  the  line,  but  brief  periodic  departures  are  manifest 
and  may  be  taken  as  truly  representing  the  extent  to  which  the  climate  departs  from  the 
mean.  The  departures,  however,  are  not  all  on  the  same  scale,  for  where  the  growth 
is  large,  the  departures  are  large,  and  vice  versa.  Hence,  they  must  all  be  reduced  to  the 
same  scale.  This  reduction  has  been  effected  by  dividing  the  numbers  used  in  figure  19 
by  the  reading  of  the  long,  straight  line  in  millimeters  for  the  corresponding  year.  By 
this  process  a  series  of  values  of  tree  growth  is  obtained  such  as  the  trees  would  give  if  they 
grew  on  the  average  a  millimeter  per  year  and  did  not  change  with  age. 


1400  '  1500  '  1600  '  noo  '  1800  '  lono 


Fig.  20. — 500-year  Curve  of  Tree  Growth — 20-year  Means. 

CLIMATIC  CYCLES. 

In  the  corrected  curve  of  growth  thus  obtained  the  minor  deviations  obscure  the  larger 
features.  Accordingly,  in  figure  20  the  curve  has  been  condensed  into  a  20-year  smoothed 
curve.  This  particular  length  of  time  was  chosen  because  a  21-year  variation  is  evident 
in  most  of  figure  19,  and  this,  as  well  as  smaller  variations,  must  be  removed  in  order  to 
leave  larger  variations  unaffected.  A  20-year  smoothed  mean  accomplishes  the  desired 
result  and  is  easier  to  calculate  than  is  a  21-year  mean.  Inspection  of  the  curve  of  figure  20 
shows  a  long  and  pronounced  maximum  of  tree-growth  between  1530  and  1620,  a  lesser 
maximum  shortly  after  1700,  and  a  still  shorter  one  at  about  1860.  Strong  minima  occur 
between  1505  and  1530,  1630  and  1675,  here  and  there  between  1740  and  1830,  and  again 
between  1870  and  1900.  Manifestly  pulsations  of  some  sort  take  place.  They  may  or 
may  not  be  permanent.  Perhaps  they  are  nothing  more  enduring  than  a  series  of  simul¬ 
taneous  wave  systems  on  a  water  surface.  Yet  for  the  navigator  a  knowledge  of  the 
existing  system  is  important;  and  so  for  the  purpose  of  weather  prediction  we  need  to  know 
the  nature  of  the  pulsations  now  existing,  and  each  one  should  be  minutely  studied.  The 
slow  changes  shown  in  the  curve  seem  to  have  a  somewhat  regular  periodicity.  In  order 
to  bring  this  out,  a  wavy  line  representing  a  cycle  of  150  years  has  been  placed  above  the 
curve  of  growth.  This  cycle  in  the  growth  of  the  trees  is  fairly  well  evident,  and  it  is 
represented  again  in  figure  21,  where  the  three  cycles  shown  in  the  main  line  of  figure  20 


1.25  mm. 
1.00  mm. 

.75  mm. 
.50  mm. 
.25  mm. 
.00  mm. 


Fig.  21. — A  Possible  150-year  Period. 


Fig.  22. — Mean  Curve  of  the  21-year  Cycle. 


118 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


have  been  placed,  one  above  another,  instead  of  consecutively.  A  cycle  of  this  length  is 
interesting,  not  only  in  itself,  but  because  it  is  one-half  of  the  period  which  Clough  thinks 
that  he  has  discovered.*  The  lower  wavy  line  in  figure  20,  representing  a  cycle  of  33.8  years, 
agrees  with  a  cycle  of  similar  length  in  the  curve  of  growth  for  the  last  180  years,  but  in 
the  years  preceding  that  time  no  such  cycle  is  apparent.  On  the  whole,  then,  the  growth 
of  these  trees  seems  to  indicate  that  a  cycle  of  this  length  is  not  here  a  permanent  feature. 
This  is  important  because  of  the  large  amount  of  discussion  in  regard  to  the  35-year  cycle 
of  Bruckner. 

In  his  “Discussion  of  Australian  Meteorology”  (South  Kensington  Solar  Physics 
Observatory,  1909),  Dr.  W.  J.  S.  Lockyer  finds  a  pronounced  19-year  cycle  in  barometric 


pressures  exhibited  in  Australia  and  South  America.  A  year  or  two  before  Lockyer’s 
publication,  I  had  worked  out  a  distinct  period  in  the  northern  Arizona  trees,  which  at 
first  seemed  to  be  19  years,  but  on  close  analysis  proved  to  be  21  years.  With  all  the 
improvements  of  method  now  made,  this  variation  is  evident  for  more  than  400  out  of  the 
500  years  and  its  length  is  21.0  years.  For  a  great  majority  of  the  time  the  crests  and 
troughs  follow  each  other  with  great  regularity.  On  the  average  the  total  variation  is  20 
per  cent  of  the  mean  (see  figures  19  and  22).  When  this  variation  is  plotted  it  shows  a 


*H.  W.  Clough:  Synchronous  Variations  in  Solar  and  Terrestrial  Phenomena.  Astroph.  Jour.,  pp.  22-42,  1905. 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


119 


very  regular  curve,  but  with  three  subordinate  minima  dividing  the  whole  into  three 
equal  parts;  this  secondary  cycle  seems  likely  to  be  due  to  traces  of  the  11 -year  period 
now  to  be  mentioned. 

The  last  cycle  to  be  considered  is  that  of  11  years.  In  the  60  years  during  which  the 
11-year  sun-spot  and  magnetic  cycle  has  been  recognized,  this  period  has  been  of  the  greatest 
interest,  for  it  deals  with  a  connection  between  the  sun  and  the  earth  other  than  gravity 
which  holds  the  earth  in  place,  and  it  indicates  that  the  energy  given  out  by  our  great 
central  luminary  is  not  constant.  Since  1873  many  writers  have  found  variations  in 
the  ordinary  meteorological  elements,  rainfall,  temperature,  and  pressure  corresponding 
to  this  period.  Hence  it  is  of  peculiar  interest  to  see  whether  the  trees  which  carry  the 
rainfall  record  back  so  far  with  a  comparatively  high  degree  of  accuracy  show  the  same 
cycle.  In  nearly  all  parts  of  the  long,  500-year  curve,  there  are  suggestions  of  an  11- 
year  variation.  By  tracing  this  throughout  the  record,  the  period  is  found  to  have  a 
length  of  very  nearly  11.4  years,  which  is  sufficiently  close  to  the  length  of  the  sun-spot 
cycle  to  be  considered  identical  with  it.  The  average  total  variation  is  16  per  cent  of  the 
mean.  The  average  conditions  of  growth  during  eight  different  intervals  of  approximately 
60  years  each  are  shown  in  figure  23.  From  this  it  appears  that  the  11-year  cycle  is  not 
uniform  throughout  the  whole  period  of  492  years  covered  by  the  curve.  In  general  the 
cycle  shows  two  maxima  and  two  minima.  From  1400  to  about  1670  the  second  minimum 
is  generally  the  deeper.  Then  from  about  1670  to  about  1790  the  cycle  flattens  out,  and 
has  no  marked  rhythmic  character.  From  about  1790  to  the  present  time  there  are  again 
two  minima,  but  here  the  first  is,  on  the  whole,  more  conspicuous. 

The  average  of  all  the  11-year  periods  from  1492  to  the  present  time  is  shown  in  the 
upper  curve  of  figure  24.  Below  this  is  the  rainfall  for  50  years  on  the  California  Coast, 


Arizona  tree  growth 
492  years 


California  coast 
rainfall-50  years 
1863-1912 


California  coast 
temperature— 50  years 
1863-1912 


Inverted  sun  spot 
numbers  125  years 


Fig.  24. — Comparison  of  11.4-year  Cycles  in  Tree  Growth,  Rainfall,  Temperature, 
and  Inverted  Sun-spot  Numbers. 


120 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  dotted  line  representing  San  Francisco,  the  dot  and  dash  line  San  Diego,  and  the 
solid  line  the  mean  of  these  two.  These  have  been  averaged  in  11-year  periods,  just  as 
have  the  measures  of  tree  growth.  Although  this  coast  is  500  miles  distant  from  the 
Arizona  trees,  and  lies  beyond  the  mountains,  yet  the  crests  and  troughs  of  the  tree  growth 
in  Arizona  correspond  closely  to  those  of  the  rainfall  in  California.  This  is  not  surprising, 
for  while  the  summer  rains  of  northern  Arizona  have  no  relation  to  the  coast  of  California, 
the  winter  precipitation  in  the  two  regions  varies  in  harmony.  Below  the  rainfall  curve 
is  placed  another,  showing  the  average  temperature  at  San  Diego  during  the  11-year 
periods  of  the  last  50  years.  Shorter  curves  of  temperature  of  other  towns  of  the  California 
coast  show  the  same  characteristics  as  that  of  San  Diego.  Here  we  find  in  the  first  half 
a  marked  similarity  to  the  rainfall  curve,  especially  to  that  of  San  Diego.  In  the  second 
half,  however,  the  temperature  curve  finds  the  minimum  satisfactorily,  but  partially  fails 
to  rise  to  the  maximum.  Thus  in  that  coast  region  we  find  exemphfied  in  the  11-year 
period  a  change  from  a  two-crested  cycle  of  rain  to  a  one-crested  cycle  of  temperature. 
This  is  not  new,  for  it  happens  every  year  in  Arizona.  That  State  has  a  double  rainy 
season,  winter  and  summer,  giving,  therefore,  a  yearly  rainfall  curve  with  two  crests. 
But  its  temperature  curve,  of  course,  has  a  high  summer  crest  only.  One  maximum  of  rain 
corresponds  to  a  maximum  of  temperature,  but  the  other  maximum  of  rain  corresponds  to 
a  minimum  of  temperature.  Dr.  Lockyer  has  worked  out  a  similar  transition  from  precipi¬ 
tation  to  pressure  in  Austraha,  and  doubtless  it  exists  in  other  subtropical  regions,  and 
probably  in  other  cycles.  The  present  case  shows  that  it  extends  outside  annual  variation. 


1820  30  40  1850  60  70  80  90  1900  1910 


Fig.  25. — Sun-spots  and  the  Growth  of  Trees  at  Eberswalde,  Germany. 


METHOD  OF  ESTIMATING  RAINFALL  BY  GROWTH  OF  TREES. 


121 


The  lowest  curve  is  an  inverted  sun-spot  curve  for  125  years,  1771  to  1896.  There 
appears  to  be  a  marked  similarity  between  this  and  the  temperature  curve.  Even  the 
subordinate  crest,  which  sometimes  shows  in  the  sun-spot  descent  from  maximum  to 
minimum,  matches  this  suppressed  second  crest  of  temperature  and  its  following  faint 
minimum.  This  would  seem  impossible  in  the  absence  of  a  real  relationship  between  them. 

The  relation  between  tree  growth  and  sun-spots  here  shown,  however  it  comes  about, 
does  not  stand  alone.  A  series  of  measures  on  13  tree  sections  from  the  forest  of  Ebers- 
walde,  near  Berlin,  Germany,  the  first  of  a  number  of  series  to  be  made  on  North  European 
pine  trees,  discloses  a  striking  time  relation  of  the  same  character.  The  13  trees  were 
divided  into  two  subordinate  groups,  given  in  curves  1  and  2  of  figure  25.  These  show 
most  satisfactory  agreement.  The  third  curve  gives  the  growth  of  the  whole  13.  The 
fourth  curve  is  the  same  as  the  third,  but  corrected  for  age.  The  fifth  curve  shows  the 
tree  growth  smoothed  in  overlapping  groups  of  three,  and  below  it  is  the  sun-spot  curve. 
The  similarity  may  be  traced  without  further  comment.  This  gives  very  strong  support 
to  the  view  here  entertained  that  there  is  a  relationship  between  the  tree  growth  and  the 
sun-spot  activity  through  the  mediation  of  the  weather. 

CONCLUSION. 

In  the  foregoing  investigation  it  has  been  shown:  (1)  that  the  variations  in  the  annual 
rings  of  individual  pine  trees  in  the  dry  regions  of  northern  Arizona  exhibit  such  uniformity 
that  the  rings  of  one  tree  can  be  identified  in  others  over  large  areas  and  the  date  of  their 
formation  established  with  practical  certainty;  (2)  that  the  ring  thicknesses  are  propor¬ 
tional  to  the  rainfall  with  an  accuracy  of  70  to  82  per  cent  in  recent  years  and  that  this 
accuracy  presumably  extends  over  centuries;  (3)  that  the  tree  year  for  such  records  begins 
in  the  autumn;  (4)  that  double  rings  are  caused  by  spring  drought  and  are  indicative  of  the 
distribution  of  rainfall  throughout  the  year;  and  (5)  that  an  empirical  formula  can  be 
made  to  express  the  relationship  between  tree  growth  and  rainfall.  The  ring  record  at 
Flagstaff,  Arizona,  has  been  traced  back  500  years  and  various  cycles  found  in  it.  An 
approximate  33-year  cycle  shows  in  the  last  200  years.  A  21-year  cycle  shows  in  400 
years  and  an  11-year  cycle  displays  a  similar  duration.  The  11-year  cycle  shows  marked 
relationship  to  the  California  coast  rainfall  and  temperature  and  to  the  sun-spot  curve. 
In  corroboration,  attention  is  called  to  the  still  more  remarkable  agreement  between  tree 
growth  in  northern  Germany  and  the  sun-spot  curve.  All  of  this  confirms  the  idea  that 
observation  of  tree  growth  may  be  a  powerful  help  in  studying  the  climate  of  the  past. 

Further  research  will  probably  show  other  and  perhaps  still  more  important  relation¬ 
ships  between  the  growth  of  vegetation,  meteorological  elements,  and  changes  in  the  sun. 
Meanwhile,  the  methods  of  computing  rainfall  from  tree  growth  must  be  still  further  per¬ 
fected.  Already,  however,  the  original  purpose  of  the  work  here  outhned  has  been  accom¬ 
plished.  Its  most  important  part,  I  hope,  has  been  the  establishment  of  a  method  of 
estimating  rainfall,  capable  of  extension  to  other  regions,  and  for  the  benefit  of  other 
branches  of  science. 


CHAPTER  XII. 

THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  GROWrH. 

In  making  use  of  the  method  of  tree  measurements  elaborated  in  the  previous  chapter 
by  Professor  Douglass,  I  have  employed  two  sets  of  data,  those  of  the  United  States  Forest 
Service  and  those  obtained  by  my  assistants  and  myself  among  the  giant  sequoias  or 
“Big  Trees”  of  the  Sierras  during  two  seasons  in  California.  The  Forest  Service,  through 
the  courtesy  of  the  Forester,  Mr.  Henry  S.  Graves,  kindly  put  at  the  disposal  of  the  Carnegie 
Institution  the  large  body  of  “stem  analyses”  which  his  Bureau  has  collected  from  forests 
in  all  parts  of  the  country.  A  stem  analysis  is  simply  the  record  of  the  measurement  of 
the  thickness  of  the  rings  of  annual  growth.  The  Forest  Service  makes  such  analyses  at 
various  points  along  the  trunks  of  trees  that  have  been  cut  for  lumber,  but  the  only  ones 
that  have  here  been  used  are  the  “stump  analyses,”  or  measurements  made  directly  upon 
the  top  of  the  cut  stump.  The  method  employed  by  the  Forest  Service  is  to  pick  out  an 
average  radius,  and  begin  measuring  from  the  outside  inward  toward  the  center.  A  finely 
graduated  ruler  is  laid  upon  the  stump  and  from  this  the  distances  are  read  off  and  recorded 
in  books  especially  prepared  for  the  purpose.  The  unit  of  measurement  is  10  years,  since 
it  is  difficult  to  measure  the  individual  years  without  an  undue  expenditure  of  time.  More¬ 
over,  for  the  purposes  of  forestry — that  is,  for  determination  of  the  rate  of  growth  of  various 
species  under  different  conditions — a  10-year  unit  is  as  good  as  a  smaller  one.  Only  in  the 
case  of  young  trees  does  the  Forest  Service  employ  the  year  as  the  unit  in  stem  analyses. 

The  measurements  which  I  obtained  in  California  were  made  in  the  same  way  as  the 
ordinary  stump  analyses  of  the  Forest  Service,  except  that  in  many  cases  the  best  radii 
were  chosen  instead  of  the  average;  these  will  be  discussed  fully  in  the  next  chapter.  At 
present  we  shall  confine  our  attention  to  the  measurements  made  by  the  Forest  Service. 
We  shall  consider  the  two  chief  ways  in  which  the  curves  obtained  by  the  simple  process  of 
averaging  need  correction  before  they  give  a  true  idea  of  the  comparative  climates  of  the 
past  and  the  present,  and  shall  elaborate  the  method  of  correcting  them,  a  method  which 
is  purely  mathematical  and  does  not  involve  the  introduction  of  the  personal  equation  to 
any  appreciable  extent.  Then  we  shall  be  prepared  to  inspect  the  curves  and  to  find  out 
what  they  indicate  as  to  our  main  problem.  The  total  number  of  analyses  which  were 
chosen  from  among  the  many  thousand  in  the  archives  of  the  Forest  Service  is  2,664. 
Only  those  of  trees  having  an  age  of  over  200  years  were  selected.  In  the  case  of  many 
species  only  a  few  specimens  reach  that  age,  and  the  number  is  not  large  enough  to  furnish 
curves  sufficiently  rehable  to  be  worth  publishing.  In  fifteen  cases,  however,  it  has  been 
possible  to  find  enough  old  trees  to  justify  the  construction  and  publication  of  their  curves. 
The  same  method  of  correction  was  employed  with  all  of  them,  except  that  in  some  cases 
one  of  the  two  corrective  factors,  which  are  to  be  discussed  later,  did  not  seem  to  apply. 

The  annual  rate  of  growth  of  trees  is  subject  to  variation  for  four  chief  reasons.  In  the 
first  place,  trees  grow  at  very  different  rates  according  to  their  age,  young  trees  usually 
growing  rapidly  and  old  trees  slowly.  In  the  second  place,  trees  destined  to  have  a  long 
life  usually  make  haste  slowly,  being  outstripped  at  first  by  their  neighbors,  which  are 
to  die  much  sooner.  These  two  types  of  variation  can  be  calculated  with  mathematical 
precision,  and  by  the  use  of  the  proper  formulae  corrective  factors  can  be  obtained  by 
means  of  which  errors  due  to  them  can  be  largely  eliminated.  The  third  reason  for  varia¬ 
tion  in  the  annual  rate  of  growth  of  trees  is  the  occurrence  of  non-climatic  accidents  such 
as  shading  in  youth,  the  breaking  of  branches,  the  slipping  of  the  soil,  the  ravages  of  insects, 
or  the  devastation  wrought  by  fire.  At  first  sight  these  appear  to  be  of  almost  preponder- 

123 


124 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


ating  importance,  but  as  a  matter  of  fact  they  play  by  no  means  so  great  a  role  as  would 
be  expected,  for,  as  Professor  Douglass  has  shown,  two  or  three  trees,  or  even  a  single 
tree,  under  exceptionally  favorable  conditions,  gives  a  fairly  accurate  climatic  record  but 
little  disturbed  by  accidents.  Finally,  the  fourth  reason  for  variation  is  the  changing 
conditions  of  weather  and  climate  which  prevail  from  year  to  year.  It  is  these  which  we 
wish  to  determine,  and  this  can  be  done  only  by  eliminating  variations  due  to  the  other 
three  causes.  Let  us  therefore  turn  to  the  problem  of  how  this  elimination  is  to  be  accom¬ 
plished.  As  accidents  are  the  matter  which  critics  of  the  method  here  discussed  are  most 
likely  to  emphasize,  let  us  take  them  up  first. 

The  elimination  of  the  effect  of  non-climatic  accidents  upon  the  rate  of  growth  of  trees 
is  accomplished  largely  by  the  process  of  averaging.  If  a  sufficient  number  of  trees  is 
used,  and  if  the  trees  are  distributed  over  a  wide  and  varied  area,  purely  individual  accidents 
will  disappear  by  the  law  of  averages.  Where  a  large  group  of  trees  is  concerned,  each  year 
— and  still  more  each  decade — is  characterized  by  about  the  same  number  of  cases  of  the 
slipping  of  the  soil,  the  crashing  of  one  tree  into  another,  the  eating  of  roots  or  buds  by 
rodents,  and  the  many  other  little  accidents  which  are  continually  checking  and  some¬ 
times  stimulating  the  growth  of  vegetation.  The  combined  effect  of  all  these  accidents  is 
a  nearly  constant  quantity.  Assurance  that  this  quantity  is  actually  constant  can  be 
obtained  only  by  using  a  sufficiently  large  number  of  measurements  distributed  over  a 
sufficiently  wide  area.  Another  type  of  accidents,  such  as  the  ravages  of  insects  and  of  fire, 
can  not  be  gotten  rid  of  quite  so  easily,  since  they  are  more  widespread  and  prevail  much 
more  abundantly  in  some  years  than  in  others.  Even  with  these,  however,  the  effect  can 
be  reduced  to  a  small  amount  by  means  of  abundant  and  widely  scattered  measurements. 
Moreover,  when  the  ravages  either  of  insects  or  of  fire  are  unusually  widespread  and 
become  regional  instead  of  purely  local  phenomena,  the  cause  is  almost  always  found  in 
unpropitious  conditions  of  climate.  Hence,  where  the  effects  of  such  ravages  can  not  be 
eliminated,  they  will  only  rarely  be  found  to  mask  the  effects  of  climate  or  prove  opposed 
to  them.  As  a  rule  they  merely  intensify  the  retardation  of  growth  which  normally 
accompanies  times  of  unfavorable  conditions  of  climate.  The  case  is  even  stronger  than 
here  appears,  but  I  shall  defer  further  discussion  of  it  until  we  have  some  actual  curves 
before  us  and  can  discuss  the  matter  in  relation  to  them. 

The  elimination  of  the  differences  in  rate  of  growth  due  to  the  fact  that  young  trees 
grow  more  rapidly  than  older  ones  is  easily  made.  A  glance  at  the  curves  prepared  by 
Professor  Douglass  and  presented  in  the  preceding  chapter  will  show  that  the  earlier 
portions  are  much  higher  than  the  later  parts.  This,  as  is  already  apparent,  does  not 
represent  a  climatic  difference,  but  is  merely  due  to  the  fact  that  trees  grow  rapidly  in 
their  youth.  Manifestly  allowance  must  be  made  for  this  varying  rate  of  growth.  I  have 
called  this  allowance  the  “corrective  factor  for  age.”  The  method  of  obtaining  it  is 
illustrated  in  the  accompanying  diagram,  figure  26.  Let  the  horizontal  line  represent  the 
course  of  time  as  indicated  in  years  by  the  figures  10,  20,  30,  40,  etc.  Let  the  vertical 
distance  indicate  the  average  thickness  of  the  ring  of  wood  added  each  year.  Suppose 
that  we  have  100  trees  varying  in  age  from  50  to  200  years.  Let  us  suppose  further  that 
we  have  averaged  up  the  rate  of  growth  of  all  these  trees  during  the  first  year  of  their 
lives  and  find  that  it  amounts  to  one-tenth  of  an  inch.  In  the  same  way  we  find  that  the 
growth  during  the  tenth  year  amounts  to  0.15  of  an  inch;  during  the  twentieth  year  0.175; 
during  the  thirtieth,  0.19;  and  the  fortieth  0.20.  After  the  fortieth  year  the  rate  of  growth 
begins  to  diminish  until  at  the  one-hundredth  year  it  has  fallen  to  a  figure  no  larger  than 
that  of  the  first,  while  at  the  two-hundredth  it  has  fallen  still  lower,  to  0.05  of  an  inch. 
Manifestly  it  is  an  easy  matter  to  plot  a  curve  from  these  figures.  The  curve  will  rise 
rapidly  at  first,  as  appears  in  figure  26,  and  then  will  fall  more  and  more  slowly.  Such  a 
curve,  when  plotted,  will  not  be  perfectly  regular,  but  will  be  somewhat  wavy,  as  shown 


THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  GROWTH. 


125 


in  the  dotted  line,  because  accidental  circumstances,  such  as  shading  in  youth,  or  periods 
of  exceptional  warmth  and  moisture  and  the  like,  will  have  caused  a  very  slow  or  very  rapid 
growth  in  certain  trees  at  certain  times.  Nevertheless  the  variations  from  a  mathematically 
perfect  curve  are  slight,  partly  because  the  number  of  trees  is  large  enough  so  that  the 
averages  are  httle  affected  by  accidents  to  individuals,  and  partly  because  of  the  fact  that 
the  first  year  of  one  tree  may  fall  150  years  before  the  first  of  another,  and  the  rest  may  be 
distributed  anywhere  between  these  two.  Thus  the  average  of  any  year,  whether  it  be  the 
first,  the  tenth,  or  the  hundredth,  does  not  represent  the  climatic  conditions  of  a  single 
year,  but  of  100  years  selected  at  random.  Thus  not  only  the  effect  of  accidents,  but 
also  that  of  climate,  is  largely  eliminated.  If  we  had  an  infinite  number  of  trees  of  all  ages, 
even  the  slight  irregularities  which  now  exist  would  be  eliminated  and  we  should  obtain  a 
smooth  curve  like  the  solid  fine  of  figure  26.  This  would  represent  the  relative  rate  at 
which  trees  of  a  given  species  would  grow  during  different  parts  of  their  life  in  the  particular 
locality  under  consideration,  provided  that  the  conditions  of  sunlight,  rainfall,  temperature, 
and  soil,  as  well  as  the  relation  of  the  plant  to  other  vegetation  and  to  accidents,  were  of 
the  average  type  and  remained  constant  during  the  life  of  the  tree. 


Fig.  26. — Ideal  Curves  illustrating  Correction  for  Age. 


If  the  curve  of  growth  of  an  individual  tree — the  dot-and-dash  line,  for  example,  in 
figure  26 — be  compared  with  the  ideal  smoothed  curve,  the  first  feature  which  strikes  the 
attention  is  the  marked  idiosyncrasies,  the  repeated  and  irregular  ups  and  downs.  So 
far  as  these  are  due  to  accidents  they  will  be  eliminated  by  averaging,  but  the  majority  are 
due  to  climatic  variations  and  form  the  essential  object  of  our  investigations.  Our  purpose 
is  to  discover  how  far  a  given  irregularity  in  one  part  of  the  curve  represents  climatic 
conditions  hke  those  giving  rise  to  a  similar  irregularity  in  another  part.  A  glance  at  the 
main  features  of  the  curve  for  an  individual  tree  shows  that  in  its  general  course  from  youth 
to  old  age  it  corresponds  to  the  ideal  smoothed  curve.  It  is  also  evident  that  in  the  portions 
of  the  curve  where  the  tree  is  growing  at  the  average  rate  of  0.20  inch  per  year,  an  increase 
of  0.10  inch  above  the  average  rate  of  growth  means  no  more  than  does  an  increase  of  0.05 
where  the  average  rate  of  growth  is  0.10.  In  both  cases  the  increase  amounts  to  50  per 
cent,  and  it  is  incumbent  upon  us  to  apply  a  corrective  factor  in  such  a  way  as  to  cause  the 
two  to  be  reckoned  as  of  the  same  value.  Mathematically  this  means  merely  that  we  must 
reduce  the  smoothed  curve,  that  is,  the  solid  line  of  figure  26,  to  a  straight  line  lying  in  a 
horizontal  position.  This  can  readily  be  done  by  selecting  some  point  as  representing 
the  standard  or  normal  growth  and  then  multiplying  the  value  of  every  other  point  on  the 
line  by  a  number  which  will  raise  or  lower  the  given  value  to  an  equality  with  the  value 
of  the  point  selected  as  the  standard.  Manifestly,  if  all  the  points  on  a  line  have  the  same 
value — that  is,  if  they  are  all  at  an  equal  distance  from  the  horizontal  base  line — the 


126 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


line  in  question  will  be  straight.  Thus  the  process  under  discussion  reduces  the  smoothed 
curve  of  growth  to  a  straight  line.  It  does  not,  however,  eliminate  the  irregular  idio¬ 
syncrasies  of  the  curve  of  an  individual  tree,  although  it  changes  their  relative  importance. 
In  the  example  under  consideration  the  average  growth  during  the  first  year  is  0.10.  Let 
us  take  this  as  the  standard  or  normal  growth.  During  the  fortieth  year  the  growth  is  0.20, 
or  twice  as  much;  to  reduce  20  to  10  means  simply  dividing  by  2.  Similarly  during  the 
two-hundredth  year  the  growth  amounts  to  0.05;  to  reduce  0.05  to  0.10  means  multiplying 
by  two.  In  other  words,  the  corrective  factor  for  age  during  the  fortieth  year  is  one-half, 
or  0.50,  while  that  during  the  two-hundredth  is  2.  Having  this  corrective  factor  for 
each  year  of  the  tree’s  hfe  we  must  apply  it  to  the  curves  of  individual  trees.  In  this  way  the 
dot-and-dash  Hne  shown  in  the  diagram  is  reduced  to  the  form  shown  by  the  dash  line  above 
it.  The  sinuosities  occur  at  the  same  time  as  before,  but  are  less  marked  than  previously 
during  the  early  years  of  the  tree’s  growth  and  more  marked  during  old  age,  when  the  tree 
was  growing  so  slowly  that  the  original  curve  became  very  flat.  In  this  final  curve  the  differ¬ 
ence  in  rate  of  growth  between  old  trees  and  young  has  no  effect.  The  variations  that  remain 
are  due  either  to  accidents,  to  climate,  or  to  another  factor  which  we  shall  now  consider. 

In  the  original  investigation  whose  results  are  here  being  set  forth,  a  puzzling  feature 
appeared  when  the  correction  for  age  was  applied  to  the  first  three  or  four  species.  In  the 
earlier  portion  of  each  curve — that  is,  in  the  part  where  only  the  oldest  trees  could  be 
used — there  was  a  systematic  lowering  of  position.  This  appeared  to  indicate  markedly 
drier  conditions  in  the  past  than  in  the  present,  but  the  apparent  difference  was  greater 
than  could  possibly  have  existed,  and  it  occurred  at  different  times  in  different  trees,  being 
dependent  apparently  on  the  age  of  that  special  species.  Moreover,  it  occurred  at  times 
when  other  lines  of  evidence  seem  to  point  to  exactly  the  opposite  state  of  affairs.  In 
attempting  to  ascertain  the  cause  of  this,  it  was  soon  discovered  that,  other  things  being 
equal,  trees  which  are  destined  to  live  to  a  ripe  old  age  grow  in  their  youth  more  slowly  than 
do  those  of  the  same  species  and  in  the  same  locality  which  are  destined  to  die  young  or 
to  live  only  until  maturity.  If  the  normal  life  of  a  species  is  200  years,  the  individuals 
which  are  to  attain  an  age  or  300  or  400  years,  almost  without  regard  to  climatic  conditions, 
grow  on  an  average  more  slowly  than  do  those  which  in  the  natural  course  of  events  are  to 
die  at  the  age  of  200  years  or  earlier.  Slow  growth  in  youth  is  apparently  one  of  the 
essential  conditions  of  a  prolonged  and  vigorous  old  age.  This  is  a  well-known  fact  when 
different  species  of  trees  are  compared.  The  fast-growing  horse  chestnut  does  not  hve 
to  anything  hke  so  great  an  age  as  the  slow-growing  oak,  but  that  this  same  law  holds  good 
within  the  species  is  not  generally  realized.  It  is  probably  not  a  universal  law,  however. 
Among  the  conifers  whose  analyses  were  obtained  from  the  Forest  Service  almost  all  the 
species  show  this  feature,  the  only  possible  exceptions  being  species  for  which  the  data 
were  insufficient  to  allow  of  its  calculation.  Among  deciduous  trees,  on  the  contrary, 
judging  from  the  few  species  yet  investigated,  there  seems  to  be  httle  difference  in  the 
rate  of  growth  of  trees  which  live  to  be  old  and  of  those  which  die  young. 

The  apparent  difference  in  rates  of  growth  between  the  old  trees  and  the  young  ones 
is  by  no  means  a  matter  of  climate  or  of  shelter  of  the  trees  during  youth.  This  is  proved 
by  the  fact  that  it  applies  to  trees  of  all  ages.  That  is,  it  makes  no  difference  whether  the 
average  hfe  of  the  species  is  100  or  300  years.  In  the  one  case  trees  which  live  to  be  150 
years  old  are  characterized  by  slow  growth  in  youth,  while  in  the  other  case  the  slow- 
growing  trees  are  those  500  years  old.  Moreover,  in  some  cases  the  difference  in  rate  of 
growth  decreases  by  regular  stages.  It  is  most  marked  in  the  first  decade,  less  marked  in 
the  second,  etc.,  and  it  commonly  disappears  or  even  is  reversed  by  the  time  the  trees  attain 
approximately  the  average  age  of  maturity.  That  is,  if  the  ordinary  age  of  a  certain  species, 
its  “three-score  years  and  ten,”  is  200  years,  the  rate  of  growth  of  the  trees  destined  to 
live  much  longer  is,  at  that  time,  no  less  than  that  of  the  others,  and  in  many  cases  more. 


THE  COKRECTION  AND  COMPARISON  OF  CURVES  OF  GROWTH. 


127 


500 


Fig.  27. — Ideal  Curve  illustrating  Correction 
for  Longevity. 


Evidently  a  “correction  for  longevity”  is  as  necessary  as  one  for  age.  It  is  applied  in 
the  same  way.  Figure  27  illustrates  the  method. 

The  horizontal  hne  in  this  case  indicates  groups  of 
trees  of  a  given  species.  Group  (A)  on  the  right  con¬ 
sists  of  trees  500  years  old,  group  (B)  of  those  400 
years  old,  (C)  300,  and  so  forth.  The  vertical  coordi¬ 
nates  represent  the  amount  of  growth  made  by  the 
trees  during  the  first  decade.  It  will  be  seen  that  the 
trees  100  years  old  made  an  average  growth  of  2  inches ; 
those  200  years  old,  1.70  inches;  300  years  old,  1.50  inches;  400  years  old,  1.35  inches;  and 
500  years  old,  1.30  inches. 

From  this  it  appears  that  if  the  minor  fluctuations  of  climate  which  took  place  from 
year  to  year  during  the  first  decade  of  the  average  tree  500  years  old  are  to  be  compared  with 
those  during  the  corresponding  decade  of  the  average  tree  200  years  old,  the  growth  of 
the  older  trees  must  be  multiplied  by  1.70  -i-  1.30  =  1.31,  the  corrective  factor  for  longevity. 
The  process  is  clearly  the  same  as  that  of  obtaining  the  corrective  factor  for  age — that  is, 
it  consists  in  multiplying  the  value  of  each  point  of  a  smoothed  ideal  curve  by  a  corrective 
factor  which  reduces  the  curve  to  a  straight,  horizontal  line.  The  determination  of  the 
corrective  factor  for  longevity,  however,  is  more  difficult  than  the  determination  of  that 
for  age,  not  because  the  factor  for  longevity  is  any  less  real  or  is  any  less  strictly  a  mathe¬ 
matical  function,  but  because  more  trees  are  required  in  order  to  secure  accuracy.  Where 
the  number  of  trees  amounts  to  200  and  the  age  does  not  exceed  more  than  300  or  400  years 
the  factor  can  be  determined  with  a  considerable  degree  of  accuracy.  For  older  trees  a 
larger  number  of  specimens  is  necessary  before  high  accuracy  can  be  obtained. 

In  considering  both  of  the  corrective  factors  it  must  be  borne  in  mind  that  they  are 
attempts  to  get  rid  of  all  variations  except  those  due  to  temporary  pulsations  of  climate. 
The  corrections  do  not  and  can  not  take  cognizance  of  any  possible  changes  of  climate 
which  may  progress  uniformly  or  continuously  from  beginning  to  end  of  the  life  of  the 
trees  in  question;  they  are  calculated  on  the  assumption  that  the  average  climate  of  the 
past  was  like  that  of  the  present.  The  attempt  is  to  smooth  the  curves  as  far  as  possible 
and  to  reduce  them  as  closely  as  may  be  to  straight  fines;  the  earliest  parts  are  thus  brought 
to  the  level  of  the  latest  in  as  great  a  degree  as  possible.  Hence  the  final  curves,  while 
showing  all  the  variations  whose  periodicity  is  less  than  that  of  the  fives  of  the  trees,  do  not 
necessarily  show  long,  secular  changes  which  may  have  taken  place.  In  many  cases,  to 
be  sure,  they  appear  to  show  them,  the  later  end  of  a  curve  being  in  general  higher  or  lower 
than  the  earlier,  but  no  reliance  can  be  placed  on  this.  It  is  generally  due  to  errors  in 
applying  the  corrective  factors,  and  these  errors  generally  arise  from  insufficiency  of  data. 

In  connection  with  the  corrections  which  have  just  been  discussed,  another  matter 
should  be  considered:  The  last  two  centuries  of  all  the  curves  of  growth  are  based  upon  a 
constant  number  of  trees.  For  earlier  dates,  the  number  gradually  diminishes,  tree  after 
tree  being  dropped  until  only  a  few  of  the  oldest  are  available.  Theoretically  the  dropping 
out  of  tree  after  tree  is  an  important  matter,  and  may  lead  to  serious  errors  unless  it  is 
guarded  against.  If  at  one  special  period  a  number  of  rapidly  growing  trees  happen  to 
drop  out,  the  curve  prior  to  that  time  will  be  relatively  too  low;  and,  in  the  same  way, 
if  all  the  trees  which  began  to  grow  at  a  given  time  happen  to  have  grown  slowly,  the  part 
of  the  curve  before  that  time  wifi  be  too  high  relative  to  the  succeeding  part.  In  order  to 
avoid  errors  of  this  sort  it  would  be  possible  to  apply  a  correction  every  time  that  a  tree  or 
group  of  trees  is  dropped  out.  In  actual  practise,  however,  I  have  found  it  inadvisable 
to  attempt  this.  Where  the  total  number  of  trees  is  ten  or  twenty  times  as  great  as  the 
number  that  is  dropped,  and  where  the  other  corrections  have  been  properly  applied,  this 
particular  correction  makes  only  slight  differences  in  the  general  form  of  the  curve. 


128 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Unless  undue  weight  is  given  to  the  vagaries  of  a  single  year,  it  demands  such  an  amount 
of  calculation  that  it  is  not  worth  attempting. 

Turning  now  from  the  method  of  obtaining  the  corrective  factors  to  their  application, 
let  us  see  how  they  work  in  actual  practise.  Let  us  take  as  an  example  the  western  yellow 
pine,  the  tree  used  by  Professor  Douglass,  and  examine  first  the  curves  upon  which  its 
corrective  factors  are  based,  and  then  the  final  corrected  curves  of  growth  for  the  last  300 
years.  The  yellow  pines  for  which  data  are  available  fall  into  two  groups:  one  from  the 
mountains  of  New  Mexico  not  far  from  the  ruins  which  were  discussed  in  previous  chapters, 
and  one  from  Idaho.  We  will  begin  with  those  from  New  Mexico.  The  figures  for  all  the 
trees  discussed  in  this  chapter,  as  has  al¬ 
ready  been  said,  were  placed  at  the  disposal 
of  the  Carnegie  Institution  of  Washington 
by  the  United  States  Forest  Service  through 
the  kindness  of  the  Forester,  Mr.  H.  S. 

Graves.  In  the  case  of  the  yellow  pine  of 
New  Mexico  the  Institution  is  indebted  to 
Mr.  A.  B.  Recknagel,  chief  of  silviculture  in  the  Forest  Service  at  Albuquerque,  New  Mexico, 
who  not  only  gathered  most  of  the  data,  but  had  them  compiled  in  his  office,  and  placed  his 
results  at  our  disposal.  His  data,  based  on  645  trees  from  four  of  the  United  States  forest 
reserves,  are  shown  in  table  3. 

The  Gila  and  Datil  national  forests  are  in  the  southwestern  paxt  of  New  Mexico  near 
the  Arizona  line,  between  the  ruins  of  the  Santa  Cruz  Valley  on  the  west,  those  of  the 
Animas  Valley  on  the  south,  and  those  of  the  Jarilla  Mountains  on  the  east.  All  three  of 
these  groups  of  ruins  are  about  150  miles  from  the  center  of  the  Gila  forest.  The  Jemez 
forest  Hes  in  the  center  of  the  northern  part  of  New  Mexico  and  adjoins  the  Pajaritan 
Plateau,  where  the  ruins  of  Tuyoni  and  the  Canyon  de  los  Frijoles  are  situated.  The  other 
reserve,  the  Zuni  forest,  is  in  northwestern  New  Mexico  about  80  miles  south  of  the  remark¬ 
able  ruins  of  the  Chaco  Canyon  and  not  much  over  30  miles  from  some  of  the  other  ruins 
described  in  preceding  chapters.  Thus  the  forests  have  approximately  the  same  distri¬ 
bution  as  the  ruins  with  which  we  have  been  deahng,  but  in  general  he  at  greater  altitudes 
than  the  ruins.  “The  measurements,”  to  quote  Mr.  Recknagel,  “were  all  taken  within 
the  western  yellow  pine  type  between  altitudes  of  7,000  and  9,000  feet.  They  were  taken 
in  the  main  body  of  the  western  yeUow  pine  type,  and  therefore  can  be  considered  as  belong¬ 
ing  to  members  of  the  pure  stand  of  the  species.”  In  other  words,  the  trees  with  which 
we  are  concerned  grew  in  the  portion  of  the  yeUow  pine  area  where  the  trees  grow  best  and 
where  they  are  neither  at  the  lower  limit,  so  as  to  be  especiaUy  liable  to  injury  by  drought, 
nor  at  the  upper  hmit,  so  as  to  be  especially  hable  to  injury  by  excessively  low  temperature 
or  long  winters.  In  general,  the  conditions  under  which  the  trees  grew  were  practically  ident¬ 
ical  with  those  described  by  Professor  Douglass  at  Flagstaff  and  the  higher  regions  around 
Prescott.  In  the  selection  of  the  analyses  to  be  used  age  was  the  only  criterion.  All  of  the 

0  25  50  75  100  125  150  175  200  225  250  275  300  325  Years 

Inches 

0.60 

0.40 


0.20 

0.00 

Fig.  28. — Curve  of  Growth  and  Correction  for  Age  of  Yellow  Pine  in  New  Mexico,  based  on 
Measurements  of  272  Trees  computed  by  Mr.  A.  B.  Recknagel.  See  Table  3a  on  page  130. 


Table  3. 


GUa. 

Jemez. 

Datil. 

Zuni. 

Total. 

Over  200  years  of  age . 

53 

10 

74 

164 

301 

Under  200  years  of  age . 

124 

19 

66 

135 

344 

Total . 

177 

29 

140 

299 

645 

THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  GROWTH. 


129 


Inches 


Date 


available  analyses  of  trees  over  200  years  of  age  have  been  used,  and  to  them  have  been 
added  an  approximately  equal  number  of  younger  trees  in  order  to  afford  fair  comparisons. 

The  results  obtained  from  the  data  furnished  by  Mr.  Recknagel  are  shown  in  figures  28 
and  29.  In  figure  28  it  will  be  seen  that  during  the  first  10  years  of  their  lives  the  trees 
on  an  average  grew  fairly 
rapidly,  or  0.46  inch  for  the 
10  years.  During  the  next 
two  decades  the  rate  of  growth 
increased  rapidly  and  reached 
a  maximum  of  0.63  inch  during 
the  third  decade.  Then  it  de¬ 
creased  rapidly  at  first,  and 
then  more  and  more  slowly 
until  at  old  age  it  had  sunk  to 
half  of  its  value  when  the  trees 
first  started.  Naturally  the 
original  curve,  the  dotted  line 
of  figure  28,  shows  a  certain 
amount  of  sinuousity  due  to 
the  various  accidents,  climatic 
and  otherwise,  to  which  the 
272  trees  which  it  represents 

have  been  subj ected.  In  order 
to  obtain  the  true  corrective  29.-Curve  of  Growth  of^r,0  Yellow  Pme^s  over  280  Years  of  Age,  from 

factor  the  curve  has  been 

smoothed  as  indicated  in  the  solid  line.  Table  3a  shows  the  measurement. 

The  use  of  the  corrective  factor  is  illustrated  in  figure  29.  In  this  case  50  of  the  oldest 
of  the  yellow  pines  of  New  Mexico  have  been  taken,  trees  that  began  growing  previous  to 
1630.  The  upper  dotted  line  shows  their  rate  of  growth  as  actually  measured;  that  is, 
before  any  correction  has  been  applied.  In  its  early  portions  for  50  years  the  curve  rises 
with  extreme  rapidity;  then  for  another  60  years  it  drops  off  almost  equally  fast;  then 
we  have  another  rise  for  30  years,  followed  by  a  fall  for  40,  a  rise  for  20,  and  so  on  to  the 
end.  The  irregularities  are  in  part  an  indication  of  fluctuations  of  growth  because  of 
climatic  variations  or  other  accidents,  but  the  main  fall  is  due  to  the  fact  that  after  1655  a.  d. 
all  the  trees  were  of  such  age  that  their  rate  of  growth  was  decreasing  in  accordance  with 
the  curve  of  figure  28.  When  the  corrective  factor  for  age  is  applied,  the  form  of  the 
curve  is  changed  greatly  and  brought  down  to  the  position  of  the  lower  dash  line.  Here  we 
find  that  the  sinuosities  continue  to  appear  at  the  same  periods  as  formerly,  but  their 
relative  size  is  changed  and  those  in  the  first  century  become  more  manifest  because 
not  masked  by  the  extremely  rapid  growth  of  youth. 

The  curve  as  thus  corrected  for  age  drops  extremely  low  in  its  early  portions.  If  no 
further  correction  were  necessary,  we  should  infer  that  climatic  conditions  were  very 
unfavorable  during  the  seventeenth  century.  The  low  position,  however,  is  due  to  the 
fact  that  no  corrective  factor  for  longevity  has  yet  been  applied. 

The  necessity  for  a  correction  for  longevity  is  illustrated  in  figure  30,  which  represents 
an  actual  case  of  the  same  kind  as  that  which  appears  in  figure  27  in  its  simplest  ideal  form. 
The  horizontal  distances  indicate  various  groups  of  trees,  varying  from  those  which  were 
only  100  years  of  age  at  the  time  of  cutting  to  a  small  group  of  three  whose  average  age 
when  cut  was  390  years.  The  age  of  the  trees  of  the  respective  groups  is  given  in  the 
upper  row  of  figures  just  under  the  letters  A,  B,  etc.  The  number  of  trees  in  each  group 
is  indicated  in  the  second  row  of  figures,  and  is  also  shown  graphically  in  the  rectangular 

10 


130 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


diagram  at  the  bottom  of  the  figure.  The  groups  of  trees  from  Q  to  U  have  been  included 
for  the  sake  of  completeness,  but  they  may  be  disregarded  not  only  because  the  number 
of  trees  in  the  last  three  groups  is  small,  but  because  all  the  trees  in  these  five  groups  are 
somewhat  abnormal  specimens,  selected  for  cutting  because  of  the  fact  that  they  had 
grown  to  large  size  in  spite  of  their  youth.  With  the  older  groups  of  trees  this  type  of 
selection  has  had  little  influence,  and  beyond  the  age  of  200  years  we  may  safely  pay  no 
attention  to  it.  Each  of  the  sinuous  lines  in  figure  30  is  comparable,  as  has  been  said, 
to  the  single  straight  line  of  figure  27.  It  represents  the  average  growth  of  each  of  the 
various  groups  during  a  particular  decade.  The  successive  lines  represent  the  growth 
during  successive  decades  up  to  the  tenth,  as  indicated  by  the 
large  figures  on  the  right-hand  side.  Then  there  is  a  skip  to  the 
fifteenth  and  another  to  the  twentieth  decade.  The  small  figures 
in  parentheses  at  either  end  of  each  line  indicate  the  dates  for 
the  particular  decade  and  group  there  represented.  The  other 
small  figures  show  how  great  a  growth  in  inches  was  made  during 
the  respective  decades  by  the  terminal  groups  of  each  curve,  that 
is,  by  group  as  shown  on  the  right  of  each  of  the  12  curves, 
and  by  group  U  for  the  first  ten  decades,  Q  for  the  fifteenth,  and 
L  for  the  twentieth,  as  shown  on  the  left.  In  each  of  the  curves 
the  actual  figures  derived  from  measurements  are  indicated  by 
the  fine  line,  while  the  heavy  line  represents  the  results  obtained 

by  smoothing  according  to  the  formula  .  The  process  of 

smoothing  is  the  simple  one  of  taking  the  average  of  three  suc¬ 
cessive  points  of  the  curve  and  plotting  it  for  the  middle  point. 

From  an  examination  of  figure  30  it  appears  that  the  oldest 
group  of  trees  began  to  grow  about  1520,  and  grew  on  an 
average  only  0.15  inch  during  the  first  decade.  The  next  group 
(A^),  which  began  fife  about  70  years  later,  grew  about  0.29  inch 
during  the  first  decade;  the  third  group,  10  years  younger,  grew 
0.41  inch;  the  fourth  group  (B)  0.45,  etc.,  until  we  come  to  the 
youngest  group  (U)  which  grew  1.03  inches.  Down  to  the  tenth 
decade  all  the  curves  have  a  distinct  slope  from  left  to  right, 
indicating  that  up  to  the  age  of  100  years  the  trees  which  are 
now  old  grew  more  slowly  than  those  which  have  not  yet  attained 
great  age,  and  most  of  which  are  not  destined  to  attain  such  age. 

By  the  time  the  fifteenth  decade  is  reached  the  difference  between  the  rate  of  growth  of 
old  trees  and  younger  trees  has  decreased  notably,  and  in  the  twentieth  decade  it  has 
disappeared.  On  the  whole  there  is  a  steady  decrease  in  the  contrast  between  old  trees 
and  young  from  the  first  decade  to  the  fifteenth  or  later.  The  object  of  the  correction  for 
longevity,  here  as  everywhere,  is  to  reduce  curves  like  those  now  under  discussion  to 
straight,  horizontal  lines.  If  the  oldest  trees  be  taken  as  the  standard,  the  greatest  correc¬ 
tion  will  be  applied  to  trees  of  group  U,  that  is,  young  trees  during  their  first  decade,  and 
the  correction  will  diminish  to  zero  with  the  oldest  group,  A^;  it  will  also  diminish  as  the 
trees  increase  in  age  until  it  becomes  zero  at  the  age  of  nearly  200  years.  In  practise  I  have 
found  it  advisable  to  treat  the  curves  as  straight,  sloping  lines  and  to  assume  that  the 
divergence  of  each  curve  from  a  straight  line  is  due  merely  to  accidents  and  to  the  fact 
that  the  number  of  trees  is  not  sufficient  to  eliminate  accidental  effects. 

Returning  now  to  figure  29,  let  us  take  the  corrective  factor  for  longevity  as  determined 
by  the  process  just  outlined  and  apply  it  to  the  curve  already  obtained  by  the  application 
of  the  other  corrective  factor,  that  is,  the  factor  for  age.  By  so  doing  we  raise  the  early  parts 


Table  3a. 


1.  Decade  of 

age  of  trees. 

2.  Average 

growth  in 

inches. 

3.  Smoothed 

average  growth 

in  inches. 

4.  Corrective 

factor  for  age. 

1 

0.46 

0.46 

0.50 

2 

0.58 

0.58 

0.39 

3 

0.63 

0.63 

0.37 

4 

0.61 

0.61 

0.38 

6 

0.57 

0.57 

0.40 

6 

0.545 

0.54 

0.43 

7 

0.495 

0.51 

0.45 

8 

0.465 

0.48 

0.48 

9 

0.445 

0.45 

0.51 

10 

0.44 

0.43 

0.53 

11 

0.415 

0.41 

0.56 

12 

0.41 

0.39 

0.59 

13 

0.385 

0.37 

0.62 

14 

0.37 

0.35 

0.66 

15 

0.335 

0.335 

0.69 

16 

0.33 

0.32 

0.72 

17 

0.325 

0.305 

0.75 

18 

0.305 

0.29 

0.79 

19 

0.275 

0.28 

0.82 

20 

0.27 

0.27 

0.85 

21 

0.28 

0.26 

0.88 

22 

0.265 

0.255 

0.90 

23 

0.24 

0.25 

0.92 

24 

0.26 

0.245 

0.94 

25 

0.25 

0.245 

0.95 

26 

0.26 

0.24 

0.96 

27 

0.265 

0.24 

0.96 

28 

0.245 

0.24 

0.97 

29 

0.25 

0.235 

0.98 

30 

0.22 

0.235 

0.98 

31 

0.225 

0.23 

0.99 

32 

0.23 

0.23 

1.00 

33 

0.23 

1.00 

THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  GROWTH. 


131 


of  the  curve,  but  leave  the  later  parts  untouched.  This  gives  the  final  curve  indicated 
in  the  solid  line.  In  this  the  sinuosities  still  occur  at  the  same  places  as  in  the  original 
upper  curve,  but  are  more  distinct  than  there.  Taken  as  a  whole  the  finally  corrected  curve 
does  not  trend  markedly  either  up  or  down,  though  the  portion  included  in  the  seventeenth 
century  is  on  the  whole  somewhat  higher  than  that  of  the  two  later  centuries. 


UTSRQPONMLKJ  IHGFEDCBA3  A2=Group 

100  120  140  160  180  200  220  240  260  280  300  310=Age  of  trees  at  cutting 

16  12  14.  37  48  62  58  33  40  29  26  38  30  29  36  26  20  17  16  16  9  6  =No.  of  trees 


Fig.  30. — Variation  in  Radial  Growth  by  Decades,  Illustrating  the  Correction  for  Longevity  of 

the  Yellow  Pine  in  New  Mexico. 

Vertical  scale:  one  small  square  equals  0.20  inch. 

Let  us  next  examine  the  other  curves  derived  from  data  furnished  by  the  United  States 
Forest  Service.  With  these  I  have  included  the  last  300  years  of  the  curve  of  the  Sequoia 
washingtoniana  based  on  nearly  200  trees  measured  in  1911.  This  may  here  be  treated 
in  the  same  way  as  the  others,  although  in  the  next  chapter  we  shall  consider  the  entire 


132 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


curve,  going  back  3,000  years  and  based  on  450  trees,  and  shall  discuss  it  in  detail.  The 
total  number  of  curves  available  for  300  years,  more  or  less,  is  17,  which  are  distributed 
from  Maine  to  California.  They  are  shown  in  figure  31.  In  most  cases  there  is  only  one 
curve  for  a  species,  although  the  yellow  pine,  red  fir,  white  oak,  and  spruce  have  two 
curves  each,  but  from  distinctly  different  localities.  An  attempt  has  been  made  to  correct 
all  the  curves  by  the  same  method  employed  in  the  case  of  the  yellow  pine.  In  certain 
cases,  however,  the  number  of  specimens  is  too  small  to  allow  of  accuracy  in  the  determina¬ 
tion  of  the  correction  for  longevity,  and  hence  it  has  been  omitted.  In  other  cases,  no 
correction  for  longevity  appears  to  be  required.  Among  the  trees  which  do  not  require 
this  correction  only  one,  the  short-leaved  pine  of  Arkansas,  is  a  conifer.  The  others — 
namely,  the  beech  of  New  York,  the  white  oak  of  Missouri,  the  white  oak  of  West  Virginia, 
and  the  tulip  poplar  of  West  Virginia — are  deciduous.  The  number  of  trees  varies  from 
26  in  the  case  of  the  white  oak  of  Missouri  and  29  in  the  case  of  the  Douglas  fir  of  Idaho 
to  728  in  the  case  of  the  white  oak  from  West  Virginia,  Kentucky,  and  Tennessee.  The 
figures  for  each  tree  are  given  in  the  diagrams  and  in  Table  H,  pages  325-327. 

The  full  significance  of  these  curves  can  not  yet  be  determined,  but  they  are  published 
here  for  the  benefit  of  future  investigators  and  because  they  enable  us  to  arrive  at  greater 
certainty  in  some  of  our  conclusions.  The  various  groups  are  arranged  partly  according 
to  place,  but  chiefly  according  to  similarity,  the  curves  at  one  extreme  being  quite  diverse 
from  those  at  the  other.  In  general  no  curve  is  wholly  different  from  those  placed  immedi¬ 
ately  beside  it,  but  the  first  and  second  groups,  although  quite  dissimilar,  have  been  placed 
beside  one  another  for  the  sake  of  contrast.  All  are  characterized  by  pronounced  fluctu¬ 
ations,  having  a  periodicity  of  100  to  200  years  or  more.  In  each  group  (excepting  the  last 
curve,  that  of  the  beech)  the  general  form  of  the  major  fluctuations  is  similar,  although 
details  differ  widely.  I  shall  at  present  make  no  attempt  to  interpret  the  curves  as  a  whole, 
for  that  is  impossible  in  view  of  the  absence  of  any  exact,  specific  measurements  of  the 
growth  year  by  year,  such  as  Professor  Douglass  has  obtained  for  the  yellow  pine,  and 
such  as  I  shall  shortly  present  for  the  sequoia.  Until  these  are  obtained  it  would  be  rash 
to  use  the  curves  as  the  basis  of  an  attempt  to  reconstruct  the  climate  of  the  United  States 
during  the  past  200  or  300  years;  for  different  species  of  trees  or  the  same  species  in  different 
habitats  may  be  stimulated  by  very  different  combinations  of  temperature  and  moisture, 
and  a  given  species  may  find  itself  equally  stimulated  by  two  diverse  combinations  of 
these  two  factors.  For  example,  to  quote  certain  facts  for  which  I  am  indebted  to  Mr. 
Raphael  Zon,  chief  of  silvics  in  the  United  States  Forest  Service,  in  regions  like  Idaho 
having  two  seasons  of  precipitation,  winter  and  summer,  the  dry  spring  is  the  critical  period. 
Therefore  the  fall  of  snow  late  in  the  winter  is  especially  beneficial.  In  regions  like  Cali¬ 
fornia,  having  no  rain  whatever  in  summer,  the  same  is  true  except  that  the  entire  amount 
of  snowfall  for  the  whole  winter  assumes  a  greater  importance.  In  regions  having  precipi¬ 
tation  at  all  seasons,  on  the  other  hand,  the  amount  of  winter  snow  makes  little  differ¬ 
ence,  provided  the  rains  of  summer,  and  especially  spring,  are  abundant.  But  all  trees  are 
not  equally  stimulated  by  such  rains,  for  some,  such  as  the  white  oak  and  tulip  poplar, 
require  warmth  as  well  as  moisture,  while  others,  like  the  beech,  seem  to  demand  only 
moisture  and  care  little  whether  the  temperature  is  above  or  below  normal. 

Before  attempting  to  draw  any  conclusions  from  the  curves,  let  us  return  to  the  question 
of  how  far  their  sinuosities  are  due  to  climatic  variations,  even  though  for  most  species 
the  nature  of  those  variations  can  not  yet  be  determined.  We  have  already  spoken  of 
the  extent  to  which  accidents,  such  as  fires,  the  shading  of  trees  during  youth,  the  ravages 
of  insects,  and  the  change  of  conditions  brought  about  by  the  white  man’s  occupation  of 
the  country,  may  have  influenced  the  shape  of  the  curves.  Now  that  we  have  them  before 
us  in  their  final  corrected  form,  it  will  be  profitable  to  consider  these  matters  once  more. 
Unquestionably,  extensive  forest  fires  not  only  kill  trees  by  the  thousand,  but  markedly 


THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  OROWTH.  133 


diminish  the  rate  of  growth  of  those  that  remain  living.  Nevertheless,  our  17  curves 
appear  to  have  been  little  influenced  in  this  way.  In  the  first  place,  previous  to  the  com¬ 
ing  of  Europeans  and  to  the  introduction  of  locomotives,  fires  were  probably  not  one-tenth 
as  numerous  as  now;  they  were  due  either  to  lightning  or  to  the  carelessness  of  the  Indians. 

197  Sequoia  washingtoniana 
California 
177  Pinus  jeffreyi 
S.  California 
107  Liriodendron 
West  Virginia 
728  Quercus  alba 
West  Virginia 


163  Picea  rubra 
Maine 

325  Picea  sp. 

West  Virginia 

29  Pseudotsuga  taxifolia 
Idaho 

217  Pinus  ponderosa 
Idaho 

68  Abies  magnifica 
California 

31  Pinus  lambertiana 
S.  California 


32  Pinus  ponderosa 
S.  California 

73  Abies  magnifica 
Idaho 

26  Quercus  alba 
Missouri 


245  Pinus  echinata 
Arkansas 


272  Pinus  ponderosa 
New  Mexico 

227  Sequoia  sempervirens 
California 


46  Fagus  grandifolia. 
New  York 


Fig.  31. — Curves  of  Growth  of  American  Trees. 

(See  Table  H,  pp.  325-327.) 

The  Indians,  however,  were  few  in  number,  and,  according  to  all  accounts,  generally  took 
great  care  to  extinguish  their  fires  or  to  kindle  them  in  places  where  they  could  not  spread. 
Still,  even  in  their  day,  there  must  have  been  a  certain  number  of  fires,  and  traces  of  these 
can  sometimes  be  seen  in  charred  spots  far  toward  the  center  of  a  great  tree.  These 
fires  must  have  produced  effects  which  are  apparent  in  some  of  our  curves.  On  the  whole, 


1600  1700  ISOO  1900 


134 


THE  CLIMATIC  FACTOK  AS  ILLUSTRATED  IN  ARID  AMERICA. 


as  we  have  already  seen,  fires  would  occur  during  dry  seasons,  and  hence  any  diminution 
of  growth  due  to  them  would  simply  accentuate  the  diminution  due  to  the  drought.  In 
spite  of  this,  however,  most  of  the  sinuosities  in  the  curves  are  apparently  not  due  to  fires. 
The  reason  for  this  conclusion  is  twofold. 

In  the  first  place,  practically  every  one  of  our  curves  is  based  upon  trees  which  did 
not  grow  in  one  restricted  locality,  but  were  spread  over  a  wide  area.  For  instance,  the 
yellow  pines  of  New  Mexico  came  from  forests  all  over  the  State;  the  white  oaks  came  from 
four  or  five  localities  in  the  States  of  Tennessee,  West  Virginia,  and  Kentucky;  and  the 
giant  redwoods  were  from  four  locahties  in  the  Sierra  Nevadas  from  5  to  60  miles  apart. 
It  is  far  from  probable  that  a  single  fire  would  affect  all  these  trees  at  once,  and  in  most 
cases  the  number  of  trees  from  a  given  locality  is  not  sufficient  to  produce  more  than  a 
slight  effect  upon  the  general  curve  unless  the  fire  were  very  widespread. 

The  second  reason  for  beheving  that  fires  have  had  no  great  effect  in  producing  the 
sinuosities  of  the  curves  is  stronger.  A  fire  causes  an  immediate  decrease  in  the  tree’s  rate 
of  growth.  It  is  followed  by  years  of  gradual  recovery.  Therefore  in  the  case  of  a  fire 
the  curve  ought  to  drop  suddenly  and  then  rise  gradually.  Sometimes  this  occurs,  but  in 
most  cases  the  drop  in  the  curves  is  not  confined  to  a  single  decade  but  continues  through 
periods  of  from  20  to  50  years.  In  a  large  number  of  cases,  a^so,  the  rise  in  the  curve  is 
more  sudden  than  the  succeeding  or  preceding  fall,  indicating  that  the  growth  of  the  trees 
received  a  somewhat  sudden  impulse,  which  was  followed  by  a  long  period  of  gradual 
decline.  Manifestly  this  is  exactly  the  opposite  of  what  would  occur  in  the  case  of  a  fire. 

Another  important  cause  of  differences  in  the  rate  of  growth  of  trees  is  the  amount  of 
sunlight  or  shade  to  which  they  are  subjected.  With  young  trees  this  is  undoubtedly  a 
matter  of  extreme  importance,  and  if  our  curves  were  based  wholly  on  immature  trees 
it  would  render  them  almost  valueless.  As  a  matter  of  fact,  however,  the  curves  are  based 
on  the  largest  trees,  those  which  for  centuries  have  been  dominant.  In  practically  all 
cases  the  first  10  years  of  the  fife  of  the  trees  are  not  used  in  our  curves,  and  in  many  cases 
a  larger  number  of  years  is  omitted.  Nevertheless  in  their  youth  the  trees  which  we  have 
employed  were  doubtless  shaded  by  other  trees.  Through  the  greater  part  of  their  lives, 
however,  they  towered  to  full  height  and  were  not  overcrowded.  Moreover,  even  if 
shading  did  prevent  normal  growth  in  a  young  tree,  after  the  trees  which  overshadowed 
such  an  individual  had  died,  other  trees  could  scarcely  grow  up  so  fast  as  to  overshadow 
it  again.  In  other  words,  the  shading  of  one  tree  by  another  might  make  the  curve  of 
growth  very  low  in  youth  and  high  in  old  age,  but  it  could  not  cause  it  to  fluctuate  back 
and  forth  from  high  to  low.  Therefore  we  must  conclude  that  while  shading  is  an  important 
factor  in  youth  and  may  largely  influence  the  beginnings  of  the  curve  of  growth  of  each 
tree  it  is  not  an  important  factor  after  maturity  is  reached. 

It  is  not  easy  to  estimate  the  ravages  of  insects.  Doubtless  they,  too,  like  fires  or 
shading,  often  check  the  growth  of  the  forests.  The  same  arguments,  however,  apply  to 
them  as  to  fires.  Their  ravages  are  apt  to  be  local  and  would  not  be  likely  to  influence 
trees  so  widely  scattered  as  those  which  we  have  used.  Moreover,  when  trees  are  attacked 
seriously  by  insects  or  other  parasites  the  chances  are  that  the  trees  so  affected  will  die, 
but  the  trees  which  have  been  used  in  our  curves  are  for  the  most  part  uncommonly  large 
and  elderly  individuals  which  show  little  sign  of  disease. 

As  to  the  effect  of  man,  little  need  be  said.  Most  of  our  curves  are  derived  from 
regions  where  man’s  influence  has  not  been  felt  until  within  a  few  years.  Even  in  long- 
settled  regions  the  sinuosities  of  the  part  of  each  curve  belonging  to  a  period  two  or  three 
centuries  ago  do  not  indicate  that  conditions  were  then  essentially  different  from  those 
which  now  prevail  after  the  coming  of  the  white  man. 

In  discussing  the  reasons  for  thinking  that  the  sinuosities  in  the  curves  are  not  of 
accidental  origin,  we  have  been  deahng  with  the  matter  negatively.  There  are,  however, 


THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  GROWTH. 


135 


distinct  positive  reasons  for  thinking  that  they  are  due  to  climatic  pulsations.  The  first 
of  these  has  already  been  given,  namely,  the  agreement  which  Professor  Douglass  finds 
between  annual  variations  in  the  rate  of  growth  of  the  yellow  pine  and  in  the  rainfall. 
Subsequent  to  the  publication  of  his  original  paper  other  investigators  have  come  to  the 
same  conclusion  in  respect  to  other  trees;  and  in  the  next  chapter  I  shall  show  how 
far  it  is  true  in  respect  to  the  Sequoia  washingtoniana  of  California.  Another  strong 
reason  for  the  belief  that  climatic  pulsations  are  the  cause  of  the  fluctuations  in  the 
curve  is  found  in  the  agreement  of  curves  for  widely  different  areas;  for  instance,  the 
curves  derived  from  32  specimens  of  the  bull  pine  of  San  Bernardino  County,  in  southern 
California,  from  73  specimens  of  the  red  fir  at  Henry’s  Lake,  Idaho,  and  from  26 
specimens  of  the  white  oak  in  Fenton,  Missouri,  all  agree  in  having  a  marked  maximum 
between  1720  and  1730  a.  d.,  a  minor  maximum  between  1770  and  1780,  and  a  second 
marked  maximum  between  1820  and  1830 — or,  in  the  case  of  the  white  oak,  a  decade 
later.  In  other  cases  there  is  a  similar  agreement:  for  example,  the  163  specimens  of  red 
spruce  from  Piscataqua  County,  Maine,  the  223  spruces  from  Nicholas  County,  West 
Virginia,  and  the  29  Douglas  firs  from  the  Salmon  Forest,  Idaho,  all  have  a  pronounced 
maximum  between  1680  and  1690  a.  d.  Next  comes  a  period  of  slow  growth,  lasting  a 
century  or  more,  but  broken  by  a  shght  maximum  about  half-way.  Then  again  the 
curves  rise,  and  reach  a  maximum  between  1810  and  1830.  On  the  other  hand,  the  white 
oak  of  West  Virginia,  with  its  728  trees,  has  its  maxima  and  minima  at  almost  opposite 
times  from  those  of  the  red  spruce  from  Maine.  In  the  same  way  the  curves  of  the  bull 
pine  of  southern  Cahfornia  and  the  Sequoia  sempervirens  from  the  northern  part  of  the 
State  are  almost  diametrically  opposed  to  one  another.  This  is  not  surprising,  for  the 
records  of  the  30  years  from  1878  to  1908  show  that  the  main  fluctuations  of  the  rainfall 
of  these  two  regions  are  in  general  the  reverse  of  one  another,  which  is  precisely  what  we 
should  infer  from  the  trees. 

The  evidence  of  these  17  curves  of  growth,  so  far  as  our  main  problem  of  climatic 
changes  is  concerned,  all  points  to  one  conclusion.  The  growth  of  trees  in  the  United  States 
seems  to  be  characterized  by  long  and  important  cycles,  having  a  periodicity  of  100  or  200 
years,  more  or  less,  and  affecting  all  parts  of  the  country.  So  widespread  a  phenomenon 
can  scarcely  be  due  to  anything  but  climate.  If  we  were  able  to  interpret  each  curve  more 
exactly  in  terms  of  rainfall,  snowfall,  drought,  temperature  and  the  like,  we  should  probably 
find  the  agreement  much  closer  than  is  now  the  case.  The  very  fact,  however,  that  curves 
from  Maine  and  Idaho,  or  from  southern  Cahfornia  and  Missouri,  agree  so  closely,  seems 
to  prove  that  climatic  pulsations  of  relatively  long  period  affect  the  whole  country  almost 
simultaneously,  and  can  be  read  in  the  trees.  It  must  not  be  inferred,  however,  that  the 
effect  is  supposed  to  be  the  same  in  all  places.  A  change  which  causes  drought  in  the  north 
may  produce  an  excess  of  moisture  in  the  south. 

The  possibihty  of  this  is  well  illustrated  in  figm-e  32,  which  shows  two  curves  for  the 


Growth  in 
inches 

0.200 


0.150 


Date  1600  1700  1800  1900 


Fig.  32. — Curves  of  Growth  of  Western  Yellow  Pine  in  New  Mexico  (dotted  line)  and  Idaho  (solid  line). 

(See  Table  H,  pp.  325-327.) 


136 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


yellow  pine,  one  in  New  Mexico  (the  dotted  line  which  we  have  already  considered)  and 
the  other  the  curve  for  217  trees  in  Idaho.  The  two  curves  were  prepared  in  exactly  the 
same  way,  and  to  both  the  corrections  for  age  and  longevity  were  applied  according  to 
the  same  mathematical  processes.  Nevertheless,  they  are  ahnost  diametrically  opposed. 
Where  one  rises  to  a  maximum  the  other  is  depressed  to  a  minimum,  and  the  opposition 
is  evident  in  practically  every  case.  Between  1600  and  1700  it  is  especially  noticeable. 
During  the  next  century,  when  climatic  conditions  were  less  extreme,  the  difference  in  the 
curves  becomes  less  marked,  and  they  run  along  together  in  a  medial  position.  Then, 
in  the  nineteenth  century,  when  drought  was  severe  in  New  Mexico,  the  two  curves  are 
again  in  marked  opposition.  Moreover,  the  general  trend  of  the  New  Mexican  curve  is 
downward,  indicating  that,  on  the  whole,  conditions  during  the  past  three  centuries  have 
become  less  favorable  to  the  growth  of  the  yellow  pine  in  that  region.  The  Idaho  curve, 
on  the  contrary,  tends  upward,  suggesting  that  conditions  have  there  become  more  and 
more  favorable.  Much  stress  must  not  be  laid  on  this  last  point,  however,  for  the  opposed 
trends  may  be  due  partly  to  errors  in  the  determination  of  the  corrective  factors. 

The  relation  between  the  two  curves  of  the  yellow*  pine  is  susceptible  of  two  inter¬ 
pretations.  In  the  first  place,  it  may  indicate  that  rainy  periods  in  New  Mexico  are  syn¬ 
chronous  with  dry  periods  in  Idaho;  or,  in  the  second  place,  it  may  mean  that  droughts 
are  synchronous  in  the  two  regions,  but  that  the  trees  of  New  Mexico,  growing  in  a  warmer, 
drier  region  than  the  others,  are  stimulated  by  long  winters,  heavy  snowfall,  and  late, 
moist  springs,  while  those  of  Idaho  are  hindered  by  the  same  conditions.  An  examination 
of  the  rainfall  of  the  two  regions  seems  to  confirm  the  first  possibility.  For  purposes  of 
comparison  I  have  taken  all  the  stations  in  Idaho,  five  in  number,  and  in  western  and 
central  New  Mexico,  including  El  Paso  on  the  border  of  Texas,  seven  in  number,  which 
have  continuous  rainfall  records  since  1894.  The  Idaho  stations  range  from  1,665  to  4,191 
feet  in  altitude,  with  an  average  altitude  of  2,700  feet.  Their  mean  annual  temperature 
ranges  from  43.4°  F.  to  51.3°  F.,  with  an  average  of  46.9°  F.  The  New  Mexican  stations 
vary  in  altitude  from  3,760  to  7,000  feet  with  an  average  of  5,150  feet,  while  their  mean 
annual  temperature  ranges  from  49.2°  F.  to  63.7°  F.  and  averages  56.5°.  In  both  cases 
the  meteorological  stations  are  2,000  to  3,000  feet  lower  than  the  region  where  the  pines 


1894  1895  1896  1897  1898  1899  1900  1901  1902  1903  1904  1905  1906  1907  1908  Year 


Fig.  33. — Rainfall  of  Idaho  (solid  line)  Compared  with  that  of  New  Mexico  (dotted  line). 


grow,  but  the  relative  conditions  are  approximately  the  same.  The  trees  of  Idaho  certainly 
grow  where  the  climate  is  cooler  and  more  rainy  than  in  the  parts  of  New  Mexico  where 
their  species  flourishes.  Nevertheless,  in  both  cases  moisture  seems  to  be  the  factor  of 
chief  importance.  Figure  33  illustrates  the  matter;  it  shows  the  average  rainfall  of  the 
five  Idaho  stations  year  by  year  compared  with  the  seven  New  Mexican  stations.  In 
only  4  cases  out  of  14  does  the  line  connecting  one  year  with  the  next  slope  the  same  way 


THE  CORRECTION  AND  COMPARISON  OF  CURVES  OF  GROWTH. 


137 


in  both  curves.  In  other  words,  when  the  rainfall  of  Idaho  increases  that  of  New  Mexico 
decreases,  and  the  reverse,  which  is  exactly  the  same  thing  that  takes  place  in  the  growth 
of  the  trees.  The  way  in  which  the  two  sets  of  curves  representing  climate  and  growth  agree 
in  presenting  opposite  phases  in  the  two  areas  goes  far  toward  proving  that  the  method  of 
Professor  Douglass  can  be  rehed  upon. 

Before  leaving  this  subject  I  would  call  attention  to  the  fact  that  while  the  precipitation 
of  New  Mexico  is  predominantly  of  the  monsoon,  summer,  or  continental  type,  and  that 
of  Idaho  is  of  the  more  northerly  type,  dependent  on  cyclonic  storms  and  falling  chiefly 
in  winter,  both  are  distinctly  of  a  mixed  type.  The  opposition  of  the  two  curves  harmon¬ 
izes  with  the  opposition  of  the  summer  and  winter  rains  at  Tucson  as  described  in  Chap¬ 
ter  I.  In  Chapter  XVI,  on  the  shifting  of  chmatic  zones,  we  come  to  the  conclusion 
that  changes  of  chmate  are  probably  characterized  by  an  alternate  strengthening  and 
weakening  of  the  earth’s  winds  by  reason  of  an  increase  or  decrease  in  the  intensity  of  baro¬ 
metric  pressure.  Such  a  strengthening  of  the  winds  would  at  first  thought  seem  to  cause 
an  increase  or  decrease  of  both  summer  and  winter  rainfall  at  the  same  period.  This, 
however,  does  not  seem  to  be  the  case  in  the  minor  variations  now  under  consideration, 
although  it  appears  to  be  true  when  we  come  to  the  larger  variations  discussed  in  Chapter 
XVI,  where  the  shifting  of  chmatic  zones  is  considered.  Possibly  this  discrepancy  is  due 
to  the  movement  of  Arctowski’s  “pleions”  and  “antipleions,”  or  areas  of  excess  or  deficiency 
of  temperature,  rainfall,  and  so  forth.  These,  as  will  be  shown  more  fully  in  Chapter  XIX, 
move  back  and  forth  in  short  periods.  They  are  located  chiefly  within  the  hmits  of  the 
United  States  and  seem  to  be  a  purely  continental  phenomenon.  Another  possibility  is 
that  Idaho  lies  so  far  north  that  the  shifting  of  zones,  which  is  discussed  hereafter,  brings 
it  into  what  is  now  the  far  northern  region  of  light  rainfall  at  a  time  when  New  Mexico 
comes  into  an  area  of  heavy  rainfall.  As  yet  the  matter  is  so  little  understood  that  any 
satisfactory  explanation  is  impossible. 

As  a  final  method  of  testing  the  value  of  the  curves  discussed  in  this  chapter,  let  us 
see  how  the  curve  for  New  Mexico  agrees  with  the  conclusions  which  we  have  already 
reached  on  the  basis  of  the  evidence  of  terraces,  archeology,  and  history.  In  this  con¬ 
nection  I  would  emphasize  the  fact  that  these  conclusions  were  all  reached  before  the 
trees  had  been  investigated.  They  have  been  set  down  in  previous  chapters  exactly  as 
they  were  reached  at  a  period  of  from  5  to  15  months  before  the  tree  measurements  were 
investigated.  The  importance  of  this  lies  in  the  fact  that  the  agreement  of  the  mathe¬ 
matically  derived  tree  curves  with  the  conclusions  derived  from  entirely  different  methods 
furnishes  strong  confirmation  of  the  accuracy  of  those  methods  as  employed  not  only  in 
America  but  in  Asia  and  southern  Europe. 

From  the  ruins  of  Gran  Quivira,  it  will  be  remembered,  we  concluded  that  at  the  time 
of  the  Spanish  occupation  of  New  Mexico  in  the  first  half  of  the  seventeenth  century 
chmatic  conditions  were  distinctly  more  favorable  than  at  present.  About  1672  the  ruins 
of  Gran  Quivira  seem  to  have  been  finally  abandoned  at  the  time  of  the  Pueblo  rebelhon. 
During  the  succeeding  century  conditions  appear  to  have  been  somewhat  better  than 
during  the  one  that  ended  in  1900,  as  appears  probable  from  the  ruins  of  Buzani  and  one 
or  two  other  places  not  here  mentioned.  Let  us  compare  the  course  of  events  thus  indicated 
with  the  final  curve  of  growth  of  the  yellow  pines  of  New  Mexico  as  derived  from  272  trees 
and  as  shown  in  the  dotted  line  of  figure  32.  The  high  parts  of  the  curve,  according  to 
the  conclusive  investigations  of  Professor  Douglass,  point  to  moist  conditions,  and  the 
low  to  dry.  If  we  interpret  the  curve  in  this  way,  it  appears  that  perhaps  one  reason 
why  the  Spaniards  were  able  to  estabhsh  themselves  in  New  Mexico  almost  without  a 
blow  was  that  from  1600  to  1650  the  amount  of  rain  and  the  general  conditions  of  the 
growth  of  vegetation  were  not  only  more  favorable  than  now,  but  were  becoming  better 
from  year  to  year.  Places  like  Gran  Quivira  were  readily  habitable  and  were  growingly 


138 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


prosperous,  so  far  as  their  prosperity  depended  upon  good  crops.  Under  such  circumstances 
the  ignorant  Pueblo  Indians  would  naturally  look  upon  the  coming  of  the  Spaniards  as  a 
blessing.  A  decrease  in  rainfall  begins  to  be  apparent  between  1650  and  1660,  but  it  is  un¬ 
important  at  first,  as  we  infer  from  the  fact  that  the  growth  of  the  trees  (and  impliedly  of  the 
crops)  continues  to  be  well  above  the  normal  until  about  1665.  Thereafter  a  rapid  deteriora¬ 
tion  takes  place,  which  culminates  about  1680  or  soon  after.  During  that  period  a  widespread 
uprising  took  place  against  the  Spaniards,  the  Pueblo  rebellion  which  ousted  the  Europeans 
for  some  years.  Doubtless  its  immediate  cause  was  the  arrogance  and  cruelty  of  some  of 
the  Spaniards,  but  back  of  that  there  probably  lay  a  deep-seated  discontent.  Want  and 
famine  must  have  prevailed,  and  if  the  Indians  were  hke  the  rest  of  mankind  they  doubtless 
ascribed  their  misfortunes  to  their  conquerors. 

The  further  elucidation  of  the  causes  of  the  Pueblo  rebellion  is  an  historical  matter 
which  can  not  be  discussed  at  this  time.  It  is  worth  while,  however,  to  mention  a  single 
piece  of  corroborative  evidence.  Mr.  E.  E.  Free  has  called  my  attention  to  an  account 
of  an  old  census  given  by  Mr.  J.  W.  Curd  in  the  El  Paso  Times.  In  this  document  there 
appears  an  interesting  reference  to  bad  crops.  El  Paso,  although  in  Texas,  lies  almost  at 
the  middle  of  the  southern  boundary  of  New  Mexico.  The  document  is  a  census  of  that 
town  dated  September  11,  1684,  and  contains  a  list  of  109  Spanish  families  living  near  El 
Paso.  It  is  signed  by  the  Spanish  governor.  To  quote  Mr.  Curd: 

“While  the  document  is  nothing  more  than  a  dry  and  uninteresting  census  roll,  it  is  illuminative 
of  the  terrible  devastation  and  suffering  that  resulted  from  the  Indian  revolt  in  1680.  This 
revolt  destroyed  some  42  presidios  and  missions  in  New  Mexico  north  of  El  Paso,  and  the  remnant 
of  Spaniards  and  friendly  Indians  took  refuge  in  Guadalupe  del  Passo  (El  Paso).  While  the 
Mission  Guadalupe  was  a  rich  one  and  additional  supplies  were  forwarded  from  Mexico  City 
the  people  still  suffered  much  from  lack  of  clothing  and  food.  The  census  shows  that  what  crops 
were  planted  that  year  consisted  only  of  maize,  which,  owing  to  drought,  was  an  almost  total 
failure.  What  maize  was  grown  was  eaten  green,  so  that  there  was  no  supply  for  winter.” 

The  full  investigation  of  this  famine  and  its  effects  must  be  left  to  the  historians.  The 
coincidence,  however,  between  the  curve  of  the  trees,  an  extraordinary  drought  and  famine, 
the  last  and  worst  stages  of  the  Pueblo  rebellion,  and  the  final  abandonment  of  places  hke 
Gran  Quivira  can  not  be  passed  unnoticed.  After  1680  conditions  appear  to  have  improved ; 
the  eighteenth  century,  although  a  period  of  less  rainfall  than  during  the  time  of  the  early 
Spanish  occupation,  was  more  propitious  than  the  century  which  has  just  closed. 


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CHAPTER  XIII. 

THE  CURVE  OF  THE  BIG  TREES. 

The  curves  of  tree  growth  thus  far  examined  all  belong  to  relatively  recent  times.  Yet 
their  length  of  200  to  300  years  suffices  to  indicate  the  existence  of  climatic  cycles  longer 
than  any  which  are  deducible  from  actual  meteorological  records;  hence  we  are  led  to 
expect  that  longer  curves  would  indicate  still  longer  cycles.  The  tree  which  gives  most 
promise  of  furnishing  a  long  curve  is  obviously  the  Sequoia  washingtoniana*  of  California. 
This  tree  is  not  only  the  largest  species  existing  at  present,  but  also  the  longest-lived,  so 
far  as  we  have  certain  knowledge.  A  few  other  species,  such  as  the  baobab,  are  known  to 
live  to  great  age,  but  as  they  are  denizens  of  tropical  countries  where  seasonal  variations 
are  slight,  they  do  not  produce  marked  annual  rings  which  can  easily  and  accurately  be 
measmed.  The  cedar  of  Lebanon  is  another  old  tree.  A  branch  of  this  which  broke  off  a 
few  years  ago  is  said  to  have  been  2,000  years  old,  according  to  a  count  of  the  rings  made 
by  an  American  member  of  the  faculty  of  the  Syrian  Protestant  College  at  Beirut.  Un¬ 
fortunately,  however,  the  number  of  really  old  cedars  is  limited  to  a  few  score,  and  it  is 
to  be  hoped  that  these  will  be  available  for  measurement  for  many  years  to  come.  In 
India,  among  the  Hima  ayas,  certain  species  of  great  age  and  size  may  eventually  give 
valuable  records,  but  they  are  not  likely  to  carry  us  back  half  as  far  as  does  the  Sequoia 
washingtoniana.  The  same  is  true  in  Australia,  although  it,  also,  has  some  old  trees  of  great 
size.  Thus  there  is  reason  to  think  that  the  sequoia  will  always  be  the  most  important 
tree  in  this  respect,  not  only  because  of  its  extraordinary  age  and  size,  but  because  a  large 
number  of  the  trees  are  readily  accessible  and  are  being  cut  year  by  year,  a  few  at  a  time, 
in  a  way  to  render  them  easily  available  for  study.  It  may  seem  a  pity  that  trees  thousands 
of  years  of  age  should  be  cut  for  fence  posts  and  “shakes,”  but  it  is  fortunate  for  our 
present  investigation.  Nor  is  it  a  matter  of  much  regret  from  the  point  of  view  of  future 
generations,  for  the  United  States  Forest  Service  has  wisely  reserved  most  of  the  areas 
where  the  trees  abound,  and  only  the  most  conservative  cutting  will  there  be  permitted. 
Moreover,  the  areas  which  are  owned  privately,  and  of  which  the  Government  can  not 
afford  to  take  possession,  revert  to  the  public  domain  as  soon  as  the  lumber  is  cut,  so  that 
as  new  trees  grow  they  will  be  preserved  for  the  future. 

A  curve  of  growth  such  as  that  of  the  Sequoia  washingtoniana  is  important  not  merely 
or  chiefly  as  a  record  of  local  climatic  conditions,  but  as  a  standard  from  which  may  be 
deduced  the  chmate  of  any  part  of  the  world  during  the  past  2,000  or  3,000  years.  Ac¬ 
cording  to  the  growing  consensus  of  opinion  among  meteorologists,  the  more  marked 
climatic  variations  of  different  parts  of  the  world  are  intimately  coordinated;  and  this 
conclusion,  as  we  have  seen,  is  confirmed  by  the  studies  of  the  present  volume.  As  yet 
the  relation  between  various  factors  in  different  parts  of  the  world,  such  as  rainfall  in 
tropical  Africa  and  winds  in  the  Sahara,  or  storms  in  central  Asia  and  the  monsoons  in 
India,  has  not  been  determined  with  precision,  but  this  is  gradually  being  accomplished. 
The  great  difficulty  lies  in  the  fact  that  exact  meteorological  records  are  nowhere  available 
for  a  period  of  much  over  a  century,  and  in  most  places  for  less  than  half  that  time.  They 

*  The  California  Big  Tree  has  often  been  known  as  Sequoia  giganlea  Endl.  That  name,  however,  is  synonymous  with 
Sequoia  semper virens,  the  redwood.  The  earliest  name  applied  to  the  Big  Tree  is  Taxodium  washingtonianum 
Winslow,  published  in  1854.  The  combination  Sequoia  washingtoniana  was  made  by  Sudworth  in  1898,  and 
this  is  the  name  that  must  stand  for  the  species.  Jepson,  in  his  Silva  of  California,  uses  for  this  tree  the 
name  Sequoia  gigantea  Decaisne,  dating  from  1854,  but  since  this  is  obviously  a  homonym  of  Endlicher’s  name, 
it  is  untenable. 


139 


140 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


do  not  cover  the  whole  of  a  single  one  of  the  longer  cycles.  Yet  long  records  are  essential 
if  we  would  understand  what  has  really  happened  in  the  past  and  thus  put  ourselves  in  a 
position  to  determine  the  cause  of  present  changes  and  to  arrive  at  the  ability  to  predict 
those  of  the  future.  Such  a  knowledge  is  equally  essential  if  we  would  understand  all  the 
varied  and  important  effects  which  climatic  pulsations,  working  through  famine,  migration, 
and  other  causes,  have  produced  upon  man  in  the  past  and  are  likely  to  produce  upon  him 
in  the  future.  Only  by  such  knowledge  of  the  past,  apparently,  and  by  the  ability  to 
predict  the  future,  can  we  be  sure  to  avoid  calamities  akin  to  some  which  have  over¬ 
whelmed  certain  portions  of  the  earth  at  various  historic  periods.  Seemingly,  then,  it  is 
not  only  of  scientific  interest,  but  of  direct  practical  value,  to  be  able  to  extend  our  climatic 
records  as  far  back  as  possible  in  all  parts  of  the  world. 

If  the  method  of  interpreting  the  growth  of  trees  introduced  by  Douglass  and  amphfied 
in  this  volume  commends  itself  to  the  scientific  world  and  is  widely  adopted,  the  work  of  a 
decade  or  two,  or  at  most  of  a  generation,  ought  to  give  us  curves  of  tree  growth  extending 
back  300  years  more  or  less  in  all  the  chief  parts  of  the  earth.  A  comparison  of  the  later 
portion  of  each  curve  with  the  local  meteorological  records  for  a  few  decades  will  show 
what  kind  of  weather  conditions  promote  or  retard  growth  and  will  enable  us  to  determine 
the  kind  of  cells  and  the  proportion  of  different  kinds  which  grow  in  years  of  particular  types. 
If  the  curves  of  several  species  are  available  from  the  same  area,  and  if  the  cellular  structure 
is  carefully  studied  in  each  case,  it  will  not  only  be  possible  to  interpret  each  curve  from 
beginning  to  end,  but  it  will  also  probably  be  feasible  to  draw  curves  representing  changes 
in  special  types  of  meteorological  phenomena,  such  as  the  amount  of  rain,  its  distribution, 
the  length  and  temperature  of  the  growing  season,  and  the  other  factors  which  are  of  chief 
importance  in  determining  the  rate  of  growth  of  vegetation.  The  curves  thus  obtained, 
being  derived  from  a  great  number  of  trees  of  several  species  scattered  over  a  considerable 
area,  will  represent  average  conditions  in  a  way  that  is  possible  only  with  a  large  number 
of  meteorological  stations.  More  important  than  this  is  the  fact  that  the  tree  curves  sum 
up  the  effect  of  all  sorts  of  meteorological  conditions  upon  vegetation.  This  effect  is  of 
paramount  importance,  as  is  clear  from  the  fact  that  the  primary  object  of  the  greatest 
weather  bureaus  is  to  furnish  statistics  and  predictions  of  weather  for  the  benefit  of  agri¬ 
culture.  Various  attempts  have  been  made  to  combine  precipitation,  temperature,  length 
of  seasons,  evaporation,  the  monthly  distribution  of  rainfall,  and  other  factors  into  a  single 
curve  which  should  sum  up  the  effect  of  the  weather  upon  plant  life,  but  the  results  have 
not  been  satisfactory.  Tree  curves,  however,  seem  to  furnish  exactly  what  is  wanted.  Of 
course  large  numbers  of  them  are  necessary,  but  the  expense  of  obtaining  them  is  not  1  per 
cent  as  great  as  the  expense  of  obtaining  reliable  meteorological  records  year  after  year. 

When  we  have  obtained  reliable  climatic  curves  for  various  parts  of  the  world  covering 
a  period  of  two  or  three  centuries,  we  shall  probably  be  in  a  position  to  make  most  instructive 
comparisons  of  one  country  with  another.  If  meteorologists  are  right  in  thinking  that  no 
great  change  in  the  circulation  of  the  atmosphere,  or  in  any  of  the  other  climatic  elements, 
can  take  place  in  one  part  of  the  world  without  a  corresponding  change  of  some  sort  in 
other  parts,  it  ought  ultimately  to  be  possible  to  say  that  a  change  of  a  certain  sort  in 
California  is  indicative  of  such  and  such  a  change  of  quite  a  different  kind  in  China,  South 
Africa,  or  some  other  part  of  the  world.  By  this  I  do  not  mean  that  minor  changes,  such 
as  those  of  a  single  year,  can  be  correlated  in  different  regions,  but  only  the  main  ones,  those 
that  belong  to  long  cycles  (such  as  Bruckner’s  35-year  cycle)  or,  still  more,  to  the  much 
greater  cycles  of  which  the  studies  of  this  volume  seem  to  furnish  evidence.  Granting, 
then,  that  a  pronounced  change  can  not  take  place  in  one  part  of  the  earth’s  atmosphere 
without  inducing  some  sort  of  variation  in  other  parts,  it  seems  to  follow  that  from  a  single 
long  curve  like  that  of  California  we  can  work  out  the  main  changes  in  all  parts  of  the  world. 
Other  lines  of  evidence  will  furnish  assistance,  and  little  by  little  the  curves  of  other  trees 


THE  CURVE  OF  THE  BIG  TREES. 


141 


will  be  carried  back  farther  and  farther;  yet  for  the  present,  and  probably  for  a  long  time 
to  come,  the  curve  of  the  Sequoia  washingtoniana  is  likely  to  be  the  most  important  of 
all  lines  of  evidence  as  to  the  chmate  of  the  last  2,000  to  3,000  years.  We  may  add  that  it 
is  hkely  to  be  one  of  the  most  important  lines  of  evidence  as  to  the  climate  of  the  future, 
for  it  will  probably  give  us  more  knowledge  of  prolonged  cycles  and  more  data  for  use  in 
the  determination  of  the  causes  of  climatic  changes  than  will  any  other  individual  group 
of  facts.  Hence  it  behooves  us  to  treat  the  subject  with  the  utmost  care  and  to  use  every 
possible  means  of  obtaining  high  accm’acy. 

The  Sequoia  washingtoniana,  as  is  well  known,  is  one  of  two  species  of  redwood,  a  genus 
which  grows  in  California,  and  nowhere  else.  The  other  species  is  the  Sequoia  semper- 
virens,  or  coast  redwood,  which  possesses  many  of  the  qualities  of  its  cousin,  the  giant 
redwood,  but  attains  neither  such  great  age  nor  such  great  size.  It  flourishes  in  the  Coast 
Range  of  California,  from  a  point  about  100  miles  south  of  San  Francisco  to  the  northern 
part  of  the  State.  It  is  never  found  at  any  great  distance  from  the  sea,  for  its  habitat  is 
limited  to  places  on  the  western  slope  of  the  mountains,  where  summer  fogs  keep  the  air 
moist  and  where  the  precipitation  is  heavy  because  the  winds  from  the  west  are  there  first 
compelled  to  rise.  The  other  redwood,  the  giant  species  with  which  we  are  mainly  con¬ 
cerned,  grows  in  a  similar  environment  among  the  Sierra  Nevadas.  Its  habitat  is  limited 
to  a  narrow  strip  250  miles  long,  beginning  near  latitude  36°,  in  the  mountains  east  of 
Portersville,  and  extending  northwest  as  far  as  latitude  39°,  w^est  of  Lake  Tahoe.  The 
trees  are  found  only  near  the  western  edge  of  the  mountains,  at  an  altitude  which  rarely 
falls  below  5,000  feet  even  at  the  northern  limits,  and  rarely  rises  above  7,000  even  in  the 
south.  In  any  given  locality  the  range  is  almost  never  more  than  1,000  feet. 

The  giant  sequoia  is  strictly  limited  to  a  narrow  band  of  abundant  precipitation.  As 
the  westerly  winds  come  from  the  Pacific  Ocean  they  first  cross  the  coastal  belt  of  cold 
water  which  prevails  along  much  of  the  California  shore.  There  they  are  so  chilled, 
especially  in  summer,  that  their  moisture  is  condensed  into  fogs.  Then  they  rise  over  the 
Coast  Range,  and  in  so  doing  are  once  more  cooled  and  obliged  to  give  up  moisture  in  the 
form  of  rain.  These  two  sources  of  moisture  make  possible  the  existence  of  the  Sequoia 
senipervirens,  but  only  in  its  own  special,  narrow  strip. 

Proceeding  eastward  the  winds  descend  into  the  inner  valley  of  California,  and  by  so 
doing  become  warm  and  capable  of  holding  much  moisture.  Hence  the  valley  is  dry, 
especially  on  the  west  side,  where  the  winds  first  descend.  Farther  eastward  the  air  is 
once  more  forced  to  rise  by  the  Sierras.  At  first  it  does  not  give  up  much  moisture,  because 
it  has  already  lost  so  much  in  crossing  the  Coast  Range.  Only  when  it  gets  to  an  elevation 
higher  than  that  reached  in  crossing  those  mountains  does  condensation  begin  to  take 
place  on  a  large  scale.  Thereafter  precipitation  increases  rapidly  for  2,000  to  3,000  feet, 
after  which  it  begins  to  decrease.  The  decrease  is  due  partly  to  the  fact  that  after  a  certain 
point  the  actual  amount  of  moisture  which  the  cooled  air  is  capable  of  holding  becomes 
slight,  and  a  large  amount  of  cooling  is  necessary  in  order  to  cause  its  precipitation,  and 
partly  because  after  a  height  of  6,000  to  7,000  feet  is  attained  the  mountains  no  longer 
rise  steeply,  so  that  the  cooling  of  the  air  is  less  rapid  than  on  the  front  of  the  mountains. 
These  various  conditions  give  rise  to  a  narrow  belt  of  heavy  rainfall  with  drier  areas  on 
either  side,  and  in  this  belt  alone  the  giant  redwood  flourishes.  Along  with  it  grow  pines 
and  cedars,  which  are  able  also  to  grow  at  both  higher  and  lower  altitudes  than  the  sequoia. 
Another  common  tree  is  the  white  fir,  which,  with  the  Douglas  fir,  is  found  in  abundance 
not  only  with  the  sequoia,  but  in  places  too  high  and  cold  for  it.  Bushes  as  well  as  great 
trees  abound  in  the  well-watered  sequoia  zone,  and  some,  like  the  azalea,  seem  to  be  almost 
as  particular  about  their  location  as  are  the  Big  Trees.  The  azaleas’  white  flowers,  tinged 
with  orange  and  pink,  are  often  banked  in  great  masses  in  the  bottoms  of  the  same  moist 
valleys  where  the  sequoia  dwells. 


142 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Every  one  has  heard  of  the  vast  size  and  great  age  of  the  Big  Trees  of  California.  The 
trunk  of  a  well-grown  specimen  has  a  diameter  of  25  to  30  feet,  which  is  equal  to  the  width 
of  an  ordinary  house.  Such  a  tree  sometimes  towers  300  feet,  or  4  times  as  high  as  a  large  elm, 
and  within  25  feet  of  the  top  the  trunk  is  still  10  or  12  feet  in  thickness.  Three  thousand 
fence-posts,  sufficient  to  support  a  wire  fence  around  8,000  to  9,000  acres,  have  been  made 
from  one  of  these  giants,  and  that  was  only  the  first  step  toward  using  its  huge  carcass. 
The  second  item  of  its  product  consisted  of  650,000  shingles,  enough  to  cover  the  roofs  of 
70  to  80  houses.  Finally,  there  still  remained  hundreds  of  cords  of  firewood  which  no  one 
could  use  because  of  the  prohibitive  expense  of  hauling  the  wood  out  of  the  mountains. 
The  upper  third  of  the  trunk  and  all  the  branches  lie  on  the  ground  where  they  fell,  not 
visibly  rotting,  for  the  wood  is  wonderfully  enduring,  but  simply  waiting  until  some  foolish 
camper  shall  light  a  devastating  fire. 

Huge  as  the  sequoias  are,  their  size  is  scarcely  so  wonderful  as  their  age.  A  tree  that 
has  lived  500  years  is  still  in  its  early  youth;  one  that  has  rounded  out  1,000  summers  and 
winters  is  only  in  full  maturity;  and  old  age,  the  threescore  years  and  ten  of  the  sequoias, 
does  not  come  for  17  or  18  centuries.  How  old  the  oldest  trees  may  be  is  not  yet  certain, 
but  during  our  two  seasons  of  field  work  in  1911  and  1912  we  counted  the  rings  of  79  that 
were  over  2,000  years  of  age,  of  3  that  were  over  3,000  years,  and  of  1  that  was  3,210  years. 
In  the  days  of  the  Trojan  War  and  of  the  exodus  of  the  Hebrews  from  Egypt,  this  oldest 
tree  was  a  sturdy  sapling,  with  stiff,  prickly  foliage  hke  that  of  a  cedar,  but  far  more  com¬ 
pressed.  It  was  doubtless  a  graceful,  sharply  conical  tree,  20  to  30  feet  high,  with  dense, 
horizontal  branches,  the  lower  ones  of  which  swept  the  ground.  Like  the  young  trees  of 
to-day,  the  ancient  sequoia  and  the  clump  of  trees  of  similar  age  which  grew  close  to  it 
must  have  been  a  charming  adornment  of  the  landscape.  By  the  time  of  Marathon  the 
trees  had  lost  the  hard,  sharp  lines  of  youth  and  were  thoroughly  mature.  The  lower 
branches  had  disappeared,  up  to  a  height  of  100  feet  or  more;  the  giant  trunks  were  dis¬ 
closed  as  bare,  reddish  columns  covered  with  soft  bark  6  to  12  inches  in  thickness;  the 
upper  branches  had  acquired  a  slightly  drooping  aspect;  and  the  spiny  foliage,  far  removed 
from  the  ground,  had  assumed  a  graceful,  rounded  appearance.  Then  for  centuries, 
through  the  days  of  Rome,  the  Dark  Ages,  and  all  the  period  of  the  growth  of  European 
civilization,  the  ancient  giants  preserved  the  same  appearance,  strong  and  solid,  but  with 
a  strangely  attractive,  approachable  quahty. 

Before  proceeding  to  more  technical  matters,  a  brief  description  of  our  method  of 
work  may  not  be  amiss.  Toward  the  end  of  May,  1911,  I  left  the  railroad  at  Sanger,  near 
Fresno,  in  the  great  inner  valley  of  California,  and  with  two  assistants  drove  up  into  the 
mountains  through  the  General  Grant  National  Park  to  Indian  Basin,  about  3  miles  west 
of  Hume,  in  a  tract  belonging  to  the  Hume-Bennett  Lumber  Company.  There  we  camped 
for  two  weeks,  and  then  went  to  a  similar  region  some  60  miles  farther  south  on  the  Tulare 
River,  east  of  Portersville,  where  we  spent  a  sHghtly  longer  time.  The  next  year,  in  early 
June,  with  Professor  H.  S.  Canby,  of  Yale  University,  and  five  student  assistants  from 
California,  I  went  again  to  the  Hume  region  and  spent  a  month  camped  at  various  points 
at  distances  of  from  2  to  10  miles  from  Hume.  After  my  departure  my  assistants  remained 
another  month  in  the  Converse  Basin.  One  of  them,  Mr.  Hiram  E.  Miller,  was  with  me 
in  both  1911  and  1912,  and  in  the  latter  year  took  charge  of  the  work  during  the  last  month. 
His  carefulness  and  efficiency  make  me  feel  as  much  confidence  in  the  results  obtained 
after  I  left  as  in  those  obtained  under  my  own  personal  supervision. 

The  method  employed  by  the  lumbermen  in  cutting  the  trees  furnishes  a  smooth  sawed 
surface  over  half  the  area  of  the  stump.  Before  the  lumbermen  attack  one  of  the  giants, 
they  build  a  platform  about  it  6  feet  or  more  above  the  ground  and  high  enough  to  be 
clear  of  the  most  flaring  portion  of  the  trunk.  On  this  two  men  stand  and  chop  out  huge 
chips  sometimes  18  inches  long.  As  the  cutting  proceeds,  a  great  notch  is  formed,  flat  on 


THE  CXJEVE  OF  THE  BIG  TREES. 


143 


the  bottom  and  high  enough  so  that  the  men  actually  stand  within  it.  In  this  way  they 
chop  10  feet  more  or  less  into  the  tree,  until  they  approach  the  center.  Then  they  take  a 
band-saw,  20  feet  or  more  in  length,  and  go  around  to  the  other  side.  For  the  next  few 
days  they  pull  the  great  saw  back  and  forth,  soaking  it  liberally  in  grease  to  make  it  slip 
easily,  and  driving  wedges  behind  it  in  order  to  prevent  the  weight  of  the  tree  from  resting 
on  the  saw.  Finally,  when  the  tree  is  almost  cut  through,  more  wedging  is  done,  and 
the  helpless  trunk  topples  over  with  a  thud  and  a  stupendous  cracking  of  branches  that 
can  be  heard  a  mile.  The  sawn  surface  exposes  the  rings  of  growth  so  that  all  one  has  to 
do  is  to  measure  them,  provided  the  cutting  has  taken  place  recently. 

Even  in  old  stumps  it  is  comparatively  easy  to  measure  the  rings.  The  sequoia  is  so 
wonderfully  durable  that  as  soon  as  one  cuts  half  an  inch  below  the  surface  of  a  stump 
the  wood  is  almost  fresh,  even  though  30  years  have  elapsed  since  the  tree  was  cut.  This, 
however,  is  true  only  of  the  heart-wood.  The  6  inches  of  wood  on  the  outside  of  each 
trunk,  that  is,  the  portion  in  which  sap  was  actually  flowing  at  the  time  of  cutting,  are  of 
quite  a  different  quality.  The  wood  is  white  instead  of  deep  red  like  the  main  body  of  the 
trunk,  it  is  soft,  and  it  decays  rapidly,  so  that  at  the  end  of  20  to  30  years  it  is  often  quite 
rotten,  although  enough  generally  remains  to  permit  the  counting  of  the  rings.  On  the 
smoothly  sawn  surface  of  the  stumps  the  rings  are  often  so  clear  that  one  can  measure 
them  easily  and  accurately  with  no  preparation  whatever,  or  else  with  no  preparation  except 
scraping  off  the  pitchy  sap  which  has  been  exuded  from  within,  or  brushing  off  an  accumu¬ 
lation  of  pine  needles  and  dirt  with  a  whisk  broom.  A  httle  experience,  however,  soon 
taught  us  that  while  the  larger  rings  could  be  measured  with  accuracy,  the  smaller  ones 
were  apt  to  be  missed  unless  greater  precautions  were  taken.  Therefore  we  made  it  a 
practise  to  chisel  grooves  an  inch  or  more  deep  in  the  more  difficult  portions  of  each  tree, 
and  in  the  latter  half  of  our  work  we  chiseled  the  entire  distance  except  for  some  of  the 
large  rings  toward  the  center.  During  the  first  season,  except  in  the  case  of  especially 
old  or  difficult  specimens,  only  one  measurement  was  made  upon  each  tree.  Our  practise 
was  to  select  the  best  possible  radius,  usually  the  longest  and  clearest,  and  always  as  free 
as  possible  from  knots.  During  the  second  year  we  invariably  measured  two  radii  on  each 
tree,  and  often  three  or  even  four.  We  also  went  back  to  many  of  the  trees  done  the  year 
before  and  measured  them  again  along  other  radii. 

One  of  our  chief  difficulties  lay  in  the  fact  that  in  bad  seasons  one  side  of  a  tree  often 
fails  to  lay  on  any  wood,  especially  in  cases  where  a  clump  of  trees  grow  together  in  the 
sequoias’  usual  habit,  and  the  inner  portions  do  not  have  a  fair  chance.  Often  we  found  a 
difference  of  20  to  30  years  in  radii  at  right  angles  to  one  another;  and  in  one  extreme  case, 
one  side  of  a  tree  3,000  years  old  was  500  years  older  than  the  other,  according  to  our  count. 
All  these  things  necessitated  constant  care  in  order  that  our  results  might  be  correct. 
Another  trial  lay  in  the  fact  that  in  spite  of  the  extraordinary  durability  of  the  wood,  a 
certain  number  of  decayed  places  are  found,  especially  at  the  centers  of  the  older  trees, 
exactly  the  portions  which  one  most  desires  to  see  preserved. 

The  net  result  of  our  work  is  summed  up  in  the  tables  on  pages  301  to  330.  From 
these  it  will  be  seen  that  we  measured  a  total  of  462  trees,  11  of  which  were  entirely  dis¬ 
carded,  because  repeated  measurements  failed  to  agree,  or  because  of  other  known  sources 
of  error.  Among  the  451  trees  actually  used,  108  were  measured  along  only  one  radius, 
234  along  two  radii,  89  along  three,  18  along  four,  and  2  along  five.  For  the  most  part 
those  measured  along  only  one  radius  were  young  trees  in  which  there  was  small  opportunity 
for  error..  A  number,  however,  were  old  trees  located  in  the  valley  of  the  Tulare  River  which 
we  visited  in  1911,  but  did  not  return  to  in  1912.  A  few  others,  located  in  regions  which 
we  revisited,  could  not  be  found  a  second  time,  or  else  could  not  be  identified  because  at 
the  beginning  of  our  work  we  failed  to  number  the  stumps,  a  practise  which  we  followed 
carefully  most  of  the  time.  The  numbers  were  chiseled  on  the  flat  surface,  and  are  there 


144 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


for  future  identification  if  other  investigators  carry  this  work  farther.  The  total  number 
of  measurements,  excluding  trees  not  used,  amounts  to  925,  which  makes  an  average  of  over 
2  for  each  tree.  Some  of  these  were  discarded,  leaving  785  as  the  number  actually  used. 

As  a  rule  three  measurements  were  made  only  in  cases  where  the  first  two  differed  by 
more  than  1  per  cent.  More  than  three  were  made  only  upon  trees  of  exceptional  difllculty. 
The  age  of  the  trees  at  the  time  of  cutting  varied  from  250  to  3,210  years.  The  average  is 
approximately  1,400.  Including  the  28  measurements  of  the  11  discarded  trees,  the  number 
of  individual  decades  measured  during  our  two  seasons  of  work  amounts  to  approximately 
111,700,  while  the  number  of  rings  actually  counted  was  ten  times  as  great,  or  1,117,000. 
So  large  a  number  of  measurements  ought  to  give  results  of  fairly  high  accuracy.  Inasmuch 
as  the  number  of  trees  which  go  back  2,000  years  is  79,  considerable  accuracy  is  possible 
at  that  remote  time;  and  even  at  a  date  600  years  earlier,  where  10  trees  are  available, 
the  results  are  sufficiently  accurate  to  indicate  the  main  outlines  of  the  climatic  curve, 
although  the  vagaries  of  individual  decades  are  not  reliable  and  the  general  fluctuations 
are  exaggerated.  Finally,  the  data  used  in  the  curve  are  derived  from  an  area  sufficiently 
wide  to  eliminate  in  large  measure  the  effects  of  purely  local  phenomena.  Most  of  the 
trees  grew  within  a  circle  10  miles  in  diameter  centering  between  Hume  and  the  General 
Grant  National  Park,  but  a  considerable  number  came  from  the  Tulare  region,  where  they 
were  distributed  in  two  tracts  8  miles  or  more  from  one  another,  and  60  miles  from  the 
main  area.  These  trees  from  the  Tulare  region  give  curves  whose  main  outlines  are  the  same 
as  those  from  the  other  area.  Therefore  it  seems  that  local  circumstances  other  than  varia¬ 
tions  of  climate  have  not  had  any  noticeable  effect  upon  the  main  form  of  the  final  curve. 

In  order  to  obtain  exact  results  it  is  necessary  not  only  to  have  a  large  number  of 
measurements,  but  to  determine  all  possible  sources  of  error  and  make  al  owances  for 
them.  In  addition  to  the  corrections  for  age  and  longevity,  which  have  been  described 
in  the  preceding  chapter,  three  other  types  of  correction  are  needed.  The  first  of  these 
is  a  correction  to  offset  the  errors  in  counting,  which  are  inevitable  if  the  counting  must 
be  done  by  fallible  human  beings.  Next  a  correction  is  required  to  offset  the  fact  that  the 
trees,  as  has  already  been  said,  do  not  always  form  complete  rings  each  year,  and  so  in 
some  cases  seem  to  be  younger  than  they  really  are.  Finally,  the  fact  that  the  trees  flare 
at  the  base,  together  with  the  fact  that  it  is  necessary  to  select  the  best  rather  than  the 
average  radii,  demands  still  another  type  of  correction. 

In  order  to  find  out  how  large  a  part  the  individual  idiosyncrasies  of  the  various 
observers  have  played  in  causing  errors  of  counting,  I  instructed  my  assistants  to  make  a 
recount  of  a  number  of  measurements.  Unfortunately  I  did  not  realize  the  necessity  of  this 
until  after  I  had  left  the  field,  and  so  my  own  error  and  that  of  four  assistants,  each  of 
whom  made  a  small  number  of  measurements,  could  not  be  determined.  For  the  three 
assistants,  however,  who  with  myself  did  four-fifths  of  the  counting,  and  measuring,  the 
statistics  are  sufficient  to  show  the  nature  and  degree  of  the  errors  involved.  The  method 
was  simple.  After  one  observer  had  finished  a  radius,  he  was  instructed  to  go  over  it  again 
and  count  the  number  of  rings,  and  his  two  fellow-observers  were  instructed  to  do  likewise. 

Table  4  shows  the  result.  In  each  case  the  number  of  radii  involved  is  46  and  the  aver¬ 
age  age  is  1,472  years.  The  first  column  shows  the  age  of  the  trees  according  to  the  original 
count.  The  other  columns  show  the  extent  to  which  the  recounts  of  the  three  observers, 
X,  Y,  and  Z,  differed  from  the  original.  It  will  be  seen  that  in  22  cases,  or  nearly  half, 
X  obtained  the  same  result  as  in  the  original  count,  which  in  many  cases  was  made  by 
himself.  In  16  cases  he  obtained  more  than  the  original,  his  greatest  divergence  being 
61  on  a  very  difficult  tree  with  small,  almost  invisible  rings,  and  his  average  divergence 
being  10.1.  In  the  remaining  cases,  8  in  number,  he  got  less  than  the  original,  his  worst 
result  being  —47,  and  his  average  —12.6.  His  divergences  on  the  plus  side  exceeded 
those  on  the  minus  side  by  only  60,  so  that  his  average  difference  from  the  original  was 


HUNTINGTON 


PLATE  6 


THE  DYING  OUT  OF  RINGS  IN  A  YOUNG  SEQUOIA  AT  DILLONWOOD 


THE  CURVE  OP  THE  BIG  TREES 


145 


only  +1,3  years.  If  the  sum  of  all  his  divergences,  whether  plus,  minus,  or  zero,  be  taken 
it  amounts  to  262,  or  an  average  of  +5.7.  This  is  a  trifle  over  0,333  per  cent  of  the 
average  age  of  the  trees.  The  net  result  is  that  in  these  46  measurements,  which  are  a 


Table  4. — The  effect  of  recounting  the  rings  of  growth  upon  the  apparent  age  of  the  sequoias  of  California. 


Difference  between  first  counts  and 

Difference  be- 

Number  of  tree 
in  table. 

Age  per 
first  count. 

recounts  of  three  observers. 

tween  read¬ 
ings  A  and 

X 

Y 

Z 

, 

B  of  tree.t 

371  A.... 

1262 

0 

-  2 

0 

1 

B.... 

1263 

0 

-  2 

-  5 

372  A.... 

1453 

0 

-  8 

-  1 

1 

B.... 

1452 

0 

-  8 

-  6 

373  A.... 

1680 

0 

-b  22 

+  22 

4 

B.... 

1676 

+  20 

+  17 

-b  26 

383  A.... 

1414 

-f-  2 

0 

-  8 

44 

B.... 

1370 

-f  22 

+  13 

0 

369  A.... 

1226 

+  61 

0 

+  76 

141 

B.... 

1367 

-  47 

-  25 

0 

410  A.... 

1893 

0 

-  31 

-  20 

51 

B.... 

1842 

0 

+  9 

-b  20 

420  A.... 

1586 

+  2 

-  5 

-  2 

21 

B 

1607 

0 

-  5 

*c.... 

426  A.... 

1450 

-  10 

1469 

0 

-  3 

-  3 

16 

B.... 

1453 

+  10 

+  13 

+  9 

413  A.... 

1289 

-  4 

-  14 

0 

B.... 

1285 

+  2 

-  2 

0 

417  A.... 

1284 

+  2 

+  3 

0 

B.... 

1288 

+  2 

-  1 

+  9 

415  A.... 

1605 

0 

-  38 

-  2 

8 

B.... 

1613 

-  6 

0 

+  11 

416  A.... 

1626 

0 

+  11 

-  10 

B.... 

1635 

+  2 

0 

+  7 

429  A. . . . 

1296 

0 

+  4 

+  6 

11 

B.... 

1285 

+  18 

+  10 

+  19 

431  A.... 

1041 

+  1 

+  2 

0 

13 

B.... 

1018 

+  3 

+  2 

0 

427  A.... 

1690 

0 

+  5 

+  1 

0 

B.... 

1690 

+  2 

0 

+  6 

432  A.... 

1349 

-  1 

+  2 

0 

1 

B.... 

1350 

-  1 

-  4 

0 

433  A.... 

2166 

0 

-  1 

+  7 

11 

B.... 

2225 

0 

+  6 

+  13 

434  A.... 

2170 

-  18 

0 

0 

19 

B.... 

2150 

-  18 

-  23 

0 

436  A.... 

1525 

0 

+  1 

-  1 

2 

B.... 

1523 

0 

-  9 

+  3 

437  A.... 

1088 

0 

+  3 

+  12 

7 

B.... 

1095 

0 

-  5 

+  3 

438  A.... 

1462 

0 

0 

+  3 

41 

B.... 

1452 

-b  10 

+  15 

0 

419  A.... 

1127 

0 

+  17 

+  1 

20 

B.... 

1138 

-  6 

0 

-  4 

428  A.... 

1270 

-1-  2 

-  7 

0 

10 

B.... 

1289 

0 

-  23 

-  24 

f  +161 

+155 

-b266) 

69487 

]  -101 

-221 

-  92  }■ 

439 

(.  ±262 

(  ±  5.7 

1  +  .13 

±376 

±  8.2 
-  1.7 

±358  J 

±  7.5  ) 

+  3.8  J 

i 

19.1 

1478 

Grand  average 

1478 

19.1 

*  This  measurement  was  made  by  mistake  at  a  part  of  the  tree  where  a  portion  of  the  outer 
rings  had  decayed.  Of  course  it  was  not  used,  but  it  is  added  here  merely  to  illus¬ 
trate  the  dangers  that  must  be  guarded  against, 
t  This  means  the  difference  between  the  apparent  age  of  the  tree  on  the  first  count  along  two 
different  radii  as  indicated  by  the  numbers  1262  for  371A  and  1263  for  371B. 

fair  sample  of  all,  the  probable  difference  between  X’s  recount  and  the  original  count  of 
himself  or  of  one  of  the  others  was  only  0.333  per  cent,  and  might  be  either  an  excess  or  a 
deficiency,  with  a  slight  tendency  toward  getting  more  rings  in  the  recount  than  in  the 
original  count.  This  tendency,  however,  amounts  to  only  0.1  per  cent.  With  Y  the 
case  is  similar,  but  as  he  was  more  careless  than  his  two  companions  his  divergence  is 
11 


146 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


greater,  8.2  years  on  the  average,  and  he  gets  shghtly  less  rings  than  they,  as  is  shown  by 
the  fact  that  his  average  divergence  when  plus,  minus,  and  zero  years  are  added,  comes 
out  a  minus  quantity.  In  the  case  of  Z,  greater  carefulness  than  with  either  of  the  others 
is  indicated  by  the  fact  that  on  the  average  his  recounts  are  0.25  per  cent  more  than 
he  and  his  companions  obtained  in  the  original  counts.  In  all  cases  the  errors  are  so 
small  that  they  can  be  neglected  without  serious  consequences. 

So  far  as  mere  errors  of  counting  are  concerned,  it  is  probable  that  in  the  long  run 
where  a  number  of  observers  are  concerned  they  balance  one  another;  but  there  is  still  a 
certain  degree  of  error  on  account  of  the  fact  that  certain  rings  are  so  small  that  they 
almost  coalesce  and  are  not  differentiated,  but  counted  as  one.  This  is  evident  from  the 
fact  that  in  general  the  more  carefully  a  radius  is  prepared  and  the  more  minutely  it  is 
scrutinized  with  a  lens,  the  greater  the  number  of  rings.  As  a  partial  offset  to  this  may 
be  put  the  fact  that  occasionally  two  rings  are  formed  in  a  single  year.  Such  cases  are  rare, 
however — far  more  rare  than  in  the  yellow  pines  examined  by  Professor  Douglass — and 
it  is  almost  invariably  easy  to  distinguish  them  by  the  lack  of  firm,  hard  fiber  in  the  outer 
portion  of  the  extra  ring,  that  is,  the  part  which  grows  late  in  the  season.  On  the  whole 
we  may  conclude  that,  so  far  as  purely  human  errors  of  counting  are  concerned,  individual 
cases  of  very  bad  trees  may  occasionally  run  as  high  as  an  error  of  5  or  6  per  cent,  but  on 
the  whole  they  are  less  than  0.333  per  cent,  and  tend  to  balance  one  another,  even  with  a 
single  observer,  and  still  more  where  several  are  concerned;  yet  there  remains  a  certain 
error,  slight,  but  constant,  due  to  the  fact  that  rings  which  actually  exist  are  not  counted. 
We  have  no  means  as  yet  of  knowing  how  great  this  is,  but  it  must  be  less  than  1  per  cent 
and  probably  not  over  0.1  per  cent,  for  in  many  trees  all  the  rings  are  so  large  that  one 
can  not  possibly  fail  to  see  them. 

The  next  source  of  error,  the  actual  absence  of  rings,  is  a  much  more  serious  matter 
than  the  errors  of  counting.  When  radii  on  different  sides  of  a  tree  are  counted  they  are 
in  many  cases  found  to  be  unequal.  The  table  of  recounts  on  page  145  shows  that  in  the 
23  trees  there  recorded  the  differences  between  the  first  and  second  readings  range  all  the 
way  from  zero  to  141,  with  an  average  of  19.1,  or  1.3  per  cent  of  the  average  age.  In  one 
exceptionally  bad  case  a  radius  on  one  side  of  an  old  tree  when  first  counted  gave  an  age 
of  3,067,  which  when  recounted  was  reduced  to  2,996,  while  a  radius  nearly  at  right  angles 
to  the  first  gave  an  age  of  2,587,  which  a  recount  reduced  to  2,526.  Such  a  divergence 
of  480  between  the  pair  of  readings  made  at  the  first  attempt  and  470  between  the  second 
pair  is  most  unusual.  It  indicates  great  irregularity,  and  this  irregularity,  in  turn,  partially 
explains  the  large  differences  of  2  or  3  per  cent  between  the  original  counts  and  the  recounts, 
differences  also  due  partly  to  the  pecuhar  way  in  which  the  stump  had  been  cut  into  the 
form  of  a  rough  cone  and  had  since  decayed  to  an  uncommon  degree.  An  inspection  of 
the  tables  at  the  end  of  the  volume  shows  that  differences  of  1  to  5  per  cent  between  different 
sides  of  the  same  tree  are  not  uncommon.  Fortunately  they  are  far  from  being  the  rule, 
since  more  than  half  of  the  trees  show  apparent  differences  of  less  than  1  per  cent,  which 
may  be  due  in  many  cases  to  errors  in  counting.  In  the  cases  where  there  is  a  genuine 
difference  it  appears  to  be  due  to  the  fact  that  during  bad  years  one  side  of  a  tree  may  not 
make  any  growth.  This  may  be  due  simply  to  the  fact  that  that  side  is  shaded  by  other 
trees  or  is  prevented  from  getting  much  nourishment  because  of  the  presence  of  great 
numbers  of  roots  of  other  plants;  or  it  may  be  due  to  injuries  such  as  the  breaking  off  of 
branches  or  the  ravages  of  fire. 

Plate  6  illustrates  an  extreme  phase  of  the  matter.  "WTien  the  young  sequoia  there 
shown  was  about  23  years  old  the  portion  about  an  inch  to  the  right  of  the  letter  A  ceased 
to  grow  for  three  or  four  years,  while  the  opposite  side  grew  as  rapidly  as  ever.  Then  the 
stunted  side  revived  and  made  a  good  growth  during  the  last  three  years  before  the  tree 
was  cut.  If  the  tree  had  continued  to  live  it  would  doubtless  have  put  on  wood  on  all 


HUNTINGTJ^ 


PLATE  7 


THE  EFFECT  OF  INJURIES  UPON  A  YOUNG  SEQUOIA, 


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THE  CURVE  OF  THE  BIG  TREES. 


147 


sides,  but  the  lost  portions  between  the  twenty-third  and  twenty-seventh  years  would 
never  have  been  replaced.  Should  such  a  tree  reach  the  age  of  3,000  years,  it  might 
well  appear  500  years  younger  on  one  side  than  the  other.  In  a  case  like  that  of  Plate  6 
it  is  an  easy  matter  to  perceive  the  loss  of  the  rings,  but  when  a  tree  becomes  large  and 
the  rings  are  not  only  very  thin,  but  have  a  length  of  from  20  to  100  feet,  as  seen  on  the 
stump,  it  is  extremely  difficult  to  follow  an  individual  ring  and  see  whether  it  dies  out  or  is 
continuous.  Occasionally  one  can  perceive  ring  after  ring  dying  out,  as  is  illustrated  at 
A  in  Plate  6.  At  other  times  this  can  not  be  seen,  but  as  the  stump  is  counted  farther 
and  farther  toward  a  given  side  the  number  of  rings  keeps  increasing.  In  stiU  other  cases 
the  loss  of  rings  is  manifest  enough  and  makes  no  difficulty.  This  is  true  in  cases  of  injury, 
such  as  burning.  It  is  illustrated  in  Plate  7,  where  the  rings  are  seen  to  tend  to  grow  out 
from  either  side  over  the  injured  portion  until  finally  they  coalesce  and  the  scar  is  no  longer 
visible  on  the  surface,  although  it  still  shows  when  the  tree  is  cut.  Where  such  scars 
exist  it  is  always  possible  to  avoid  them  in  measuring,  but  in  trees  which  have  been  sub¬ 
jected  to  many  injuries,  in  order  to  avoid  them,  the  measuring  must  be  done  upon  fines  which 
zigzag.  In  such  cases  the  rings  vary  in  width  more  than  would  be  the  case  if  only  climatic 
causes  were  active.  Such  trees  were  in  general  avoided  in  our  measurements,  although  a 
few  were  included,  because  they  were  of  unusual  age.  Trees  which  have  lost  rings  in  the 
other,  less  noticeable  fashion  can  not  so  easily  be  detected  or  avoided,  inasmuch  as  two 
counts  are  necessary  before  their  character  becomes  evident.  Even  then  one  can  not 
be  sure  that  the  error  is  really  in  the  tree  and  not  in  the  observer  until  a  third  count  has 
been  made.  Cases  where  three  or  more  counts  proved  highly  divergent  were  rejected  in 
our  final  computations.  Usually,  however,  a  fair  degree  of  agreement  was  found.  In  the 
majority  of  cases  the  first  two  readings  were  in  such  close  agreement  that  both  could  be  used. 
Nevertheless,  differences  of  1  or  2  per  cent  are  common.  In  such  cases  we  have  assumed 
that  the  larger  value  comes  nearer  to  representing  the  true  age. 

From  what  has  just  been  said,  it  is  evident  that  while  many  trees  have  the  full  number 
of  rings  on  all  sides,  many  others  show  deficiencies.  Hence  it  is  impossible  to  be  sure  of 
the  exact  age  of  any  tree  unless  measurements  are  made  on  all  sides.  With  trees  having  a 
diameter  of  10  to  20  feet  or  more,  and  numbering  their  rings  by  the  thousand,  this  is 
practically  an  impossibility  because  of  the  expense  and  time  involved.  If  a  small  number 
of  measurements,  one,  two,  or  three,  are  made  upon  each  tree  at  places  determined  by 
the  accidents  of  cutting  and  of  smooth,  clean,  easily  read  radii,  there  is  bound  to  be  a 
deficiency  in  the  apparent  as  compared  with  the  real  age  of  the  trees.  In  individual  cases 
the  radii  having  the  maximum  number  of  rings  will  happen  to  be  counted  and  the  true 
age  will  be  obtained.  In  the  best  trees,  those  which  do  not  have  the  habit  of  dropping  any 
rings,  this  will  happen  continually.  With  the  other  trees  it  will  happen  only  rarely,  and 
thus  in  any  large  group  there  is  sure  to  be  an  error.  This  error  can  not  be  calculated 
exactly,  since  there  is  no  known  rule  as  to  how  much  of  a  given  ring  is  lost  and  how  much 
retained.  If  we  make  an  assumption  as  to  this  matter,  however,  the  rest  can  readily  be 
calculated.  Let  us  assume  that  conditions  are  like  those  in  figure  34.  Here  the  age  of 
the  tree  is  supposed  to  be  100  years.  In  the  half  of  the  trunk  indicated  by  the  letters 
Ab  A^,  and  A®  all  the  rings  are  complete.  In  the  other  half  they  die  out  at  regular  intervals, 
until  the  minimum  is  reached  at  B,  half-way  between  A^  and  A®,  the  two  points  where  the 
maximum  comes  to  an  end.  This  will  be  readily  seen  from  the  diagram,  where  the  number 
of  rings  at  the  minimum  is  assumed  to  be  76.  Suppose,  now,  that  only  one  radius  were 
measured  in  an  infinite  series  of  trees  of  this  kind.  This  radius  would  fall  at  all  possible 
positions,  as  chance  might  dictate.  Half  of  the  time  it  would  have  the  maximum  value 
of  100  rings.  During  the  rest  of  the  time  it  would  vary  from  100  to  76,  with  an  average 
value  of  88.  Hence  the  average  of  all  the  readings  would  be  the  mean  of  88  and  100, 
or  94,  which  is  less  than  the  true  maximum  by  6,  or  by  one-fourth  of  the  difference  between 


148 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  true  maximum  and  the  true  minimum.  Expressed  in  general  terms  this  means  that 
if  half  of  the  trunk  has  the  full  number  of  rings,  and  if  the  number  diminishes  regularly 
to  a  minimum  at  a  single  point,  an  average  measurement  will  be  less  than  the  maximum  by 
one-fourth  of  the  difference  between  the  maximum  and  the  minimum. 

Suppose  now  that  two  radii  be  measured  and  that  the  angle  between  them  be  180° — 
that  is,  suppose  that  they  lie  opposite  one  another;  in  this  case  one  of  the  radii  will  always 
have  a  value  of  100,  so  that  the  average  value  of  the  apparent  maximum  will  be  equal  to 
the  true  maximum.  The  value  of  the  minimum,  on  the  other  hand,  will  fluctuate  between 
100  and  76,  and  its  average  will  be  88. 


Fig.  34. — Ideal  Diagram  to  Illustrate  the  Dropping  of  Rings. 

In  actual  practise,  where  two  measurements  are  taken,  it  is  not  possible  to  have  them 
in  line  with  one  another.  This  is  due  to  the  fact  that  the  trees,  as  has  already  been  ex¬ 
plained,  are  not  sawed  entirely,  but  are  chopped  through  half  their  thickness.  Only  the 
sawed  part  can  be  measured  with  ease  and  accuracy.  Hence,  in  the  choice  of  places  for 
measurement,  we  are  limited  to  180°.  The  distance  of  the  radii  from  one  another  varies 
from  90°,  or  occasionally  even  less,  up  to  180°,  according  to  the  exigencies  of  the  trunk  in 
question.  On  an  average,  the  distance  is  about  135°.  In  such  a  case,  it  is  evident  that 
the  two  radii  will  be  equal  when  they  lie  anywhere  in  the  portion  of  the  tree  A^A^A^,  or 
in  the  positions  XO  and  FO  at  a  distance  of  22.5°  from  the  line  where  the  number  of  rings 
ceases  to  be  the  maximum.  Evidently  the  maximum  line  can  never  lie  in  the  sector  of  the 
tree,  135°  in  extent,  between  X  and  Y,  but  must  lie  somewhere  in  the  sector  XA^Y.  This 
part  consists  of  180°  having  a  value  of  100  and  45°  whose  value  ranges  from  100  to  94.  The 
average  value  of  this  latter  portion  is  97.  Therefore,  the  average  value  of  all  the  maximum 
radii  which  could  possibly  be  obtained  when  the  two  radii  are  135°  apart  would  be  99.4. 

The  value  of  the  minimum  radii  may  be  calculated  in  the  same  way.  Manifestly,  the 
minimum  can  never  lie  in  the  portion  of  the  tree  MA^N,  but  must  lie  in  the  portion 
MBN.  The  average  value  of  this  latter  portion  amounts  to  90.4.  The  difference  between 
the  average  maximum  and  the  average  minimum  readings  is  9,  which  is  9  per  cent  of  the 


THE  CURVE  OF  THE  BIG  TREEvS. 


149 


true  maximum — that  is,  of  the  actual  age  of  the  tree.  By  comparison  of  the  first  and 
second  readings  of  the  trees  actually  measured,  it  is  easy  in  any  given  group  to  compute 
this  difference  between  the  average  maximum  and  the  average  minimum.  Its  value  for 
all  our  sequoias  is  shown  in  table  5.  There  it  will  be  seen  that  for  trees  under  1,000  years 
old  it  amounts  to  about  0.73  per  cent.  As  the  trees  grow  older  it  increases,  until  with 
trees  more  than  2,000  years  old  it  becomes  1.62  per  cent.  Thus  it  appears  that  as  a  tree 
grows  older  the  liability  to  loss  of  rings  increases,  so  that  a  tree  2,000  years  old  is  not  only 
likely  to  have  lost  twice  as  many  rings  as  a  tree  1,000  years  old,  because  it  is  twice  as  old, 
but  this  loss  is  likely  to  have  been  doubled.  This  greater  proportion  of  loss  among  the  old 
trees  is  due,  apparently,  to  the  fact  already  discussed,  that  the  trees  which  live  to  a  great 
age  grow  slowly  in  their  youth.  They  are  hard,  knotty  trees,  able  to  resist  drought,  and  per¬ 
haps  not  suffering  by  the  loss  of  a  year’s  growth  so  much  as  do  trees  which  grow  rapidly. 


Table  6. — The  difference  between  the  first  and  second  measurements  of  sequoias. 


Age  of  trees  in  years. 

Average  age 
of  trees  in 
years. 

No.  of  trees. 

Difference  1 

n 

Sum. 

)etween  first 
leasurementi 

Average. 

and  second 

i. 

Percentage 
of  average 
age. 

A.  250-1000 

640 

115 

536 

4.65 

0.73 

B.  1000-2000 

1470 

257 

4202 

16.35 

1.11 

C.  over  2000 

2285 

79 

2914 

36.90 

1.62 

The  percentages  given  in  table  5  enable  us  to  form  an  estimate  of  the  degree  of  accuracy 
which  we  have  probably  obtained  in  determining  the  age  of  our  trees.  If  we  assume  that 
half  of  each  tree,  on  an  average,  shows  the  correct  number  of  rings,  the  ratio  of  the  per¬ 
centage  of  rings  missing  to  the  average  difference  between  the  maxmum  and  minimum 
measurements  will  be  24  to  9.  In  group  A  of  the  table,  the  average  age  of  the  trees  is  640 
years.  The  average  difference  between  the  first  and  second  readings  amounts  to  0.73  per 
cent.  From  this  we  can  deduce  the  equation,  24  :  9  :  ;  X  :  0.73.  In  this  case,  X  is  the 
percentage  of  difference  between  the  absolute  maximum  and  absolute  minimum  of  the 
trees  in  group  A.  Its  value  is  1.94  per  cent,  and  this  percentage  of  640  equals  approxi¬ 
mately  12  years.  This  means  that,  according  to  the  assumption  made  above,  the  average 
tree  under  1,000  years  old  misses  12  rings  at  some  point  in  its  circumference. 

In  order  to  find  how  nearly  the  supposed  maximum  approximates  the  actual  maximum, 
another  equation  is  necessary.  In  the  assumed  case  of  figure  34,  the  average  maximum 
amounts  to  99.4  per  cent  of  the  absolute  maximum,  and  is  less  than  it  by  0.6  per  cent. 
The  difference  between  absolute  maximum  and  absolute  minimum  is  24.  The  ratio  of 
24  to  0.6  equals  that  of  12  to  F,  in  which  Y  is  the  number  of  years  by  which  the  average 
measured  maximum  in  trees  under  1,000  years  of  age  is  less  than  the  average  absolute 
maximum.  F,  it  will  be  seen,  amounts  to  0.3,  or  less  than  half  a  year. 

In  the  same  way  it  is  possible  to  calculate  the  number  of  years  by  which  the  maximum 
reading  of  trees  of  any  age  will  be  less  than  its  true  value.  Even  in  the  case  of  the  oldest 
group  of  trees  this  amounts  to  only  about  4  years,  or  0.166  per  cent  of  the  age.  This  is 
so  small  a  number  that  it  can  be  neglected,  and  in  cases  where  two  or  more  readings  are 
available  we  can  assume  that  the  error  arising  from  the  loss  of  rings  is  no  greater  than 
the  error  due  to  mistakes  in  counting. 

Where  only  one  reading  is  available,  however,  the  case  is  quite  different.  In  the  ideal 
case  of  figure  34,  an  average  reading  is  6  per  cent  less  than  the  true  maximum;  6  per  cent 
is  two-thirds  of  the  9  per  cent  which  we  have  seen  to  be  the  average  amount  by  which 
the  maximum  and  minimum  readings  differ  from  one  another  if  the  two  lines  of  measure¬ 
ment  be  135°  apart.  If  we  apply  this  ratio  to  the  percentages  of  table  5,  we  find  that  in 
trees  under  1,000  years  of  age  the  average  reading  is  less  than  the  true  maximum  by  0.48 
per  cent,  while  in  the  oldest  group  of  trees  it  is  less  by  1.08  per  cent. 


150 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


From  this  it  appears  that  if  we  would  obtain  correct  results  from  our  measurements  of 
trees,  it  is  necessary  to  make  a  slight  addition  in  those  cases  where  only  one  reading  is 
available.  The  amount  of  this  addition  can  be  seen  in  tables  C  and  D,  on  pages  302-307. 
It  varies  from  a  negligible  quantity  with  the  youngest  trees  to  as  much  as  four  or  five  decades 
with  the  oldest  trees.  In  making  the  computations  upon  which  our  final  tree  curve  has  been 
based,  additions  of  this  sort  have  been  made — that  is,  in  cases  where  only  a  single  measure¬ 
ment  of  a  tree  was  available  there  has  been  added  a  sufficient  number  of  decades  to  bring 
the  age  up  to  the  maximum,  according  to  the  assumption  just  set  forth.  The  extra  decades 
have  been  inserted  at  equal  intervals  from  beginning  to  end  of  the  tree’s  fife.  They  have 
in  every  case  been  given  the  mean  value  of  the  decades  on  either  side  of  them. 

In  addition  to  this,  decades  have  been  added  to  certain  measurements  for  another 
reason.  Where  two  or  more  measurements  of  a  single  tree  are  available  I  have  assumed 
that  the  maximum  reading  is  nearly  correct,  and  have  added  enough  decades  to  the  other 
reading  or  readings  to  bring  them  to  the  same  age.  The  decades  have  been  distributed  evenly 
from  beginning  to  end  of  the  tree’s  fife,  as  in  the  other  case.  Where  the  difference  between 
the  readings  amounts  to  more  than  2  per  cent,  only  the  maximum  reading  has  been  used. 

Average  growth 


Fig.  35. — Sequoia  washingloniana :  Corrective  Factor  for  Age  during  first  250  Years  of  Life, 

plotted  by  Decades.  (See  Table  A,  p.  301.) 


The  object  of  all  these  changes  is  to  give  each  tree  its  correct  age  as  nearly  as  possible 
and  to  prevent  the  curve  from  flattening  out.  Suppose  that  a  period  of  rapid  growth  took 
place  in  a  tree  2,000  years  ago  and  lasted  two  or  three  decades;  if  one  measurement  of  this 
tree  gives  it  an  age  of  2,500  years  and  another  measurement  gives  only  2,450,  or  2  per  cent 
less,  it  is  clear  that  the  period  of  rapid  growth  2,000  years  ago,  as  indicated  by  the  two  radii, 
will  come  earlier  in  one  case  than  in  the  other.  The  result  will  be  that  when  the  two  are 
averaged  it  will  not  be  so  evident  as  it  ought,  for  by  being  spread  over  a  long  interval  it 
will  be  reduced  by  half  its  value,  and  will,  in  turn,  raise  places  which  ought  to  be  low. 

From  what  has  been  said  in  regard  to  this  correction  for  missed  rings,  it  may  appear  as 
if  by  applying  it  we  should  introduce  large  changes  into  our  final  curve;  but  as  a  matter 
of  fact  the  total  number  of  decades  added  to  all  the  785  measurements  of  our  451  trees 
amounts  to  only  405.  The  total  number  of  decades  indicated  by  all  the  measurements  of 
these  trees  is  111,700,  so  that  the  total  change  in  the  curve  amounts  to  less  than  0.4  per  cent. 
The  maximum  effect  is,  of  course,  produced  in  the  oldest  trees.  The  part  of  the  curve 
less  than  1,000  years  of  age  is  practically  unaffected.  From  that  point  backward,  the  effect 
increases,  but  even  at  2,000  years  of  age  it  amounts  to  only  8  years;  a  maximum  which, 
according  to  the  uncorrected  curve,  would  occur  at  100  b.  c.,  according  to  the  corrected 
curve  occurs  at  108  b.  c. 

The  corrections  for  age  and  longevity  are  very  different  from  those  that  we  have  just 
been  considering.  Instead  of  producing  a  small  and  almost  unnoticeable  effect,  they 
greatly  change  the  form  of  the  curve.  The  methods  used  in  obtaining  them  have  already 


THE  CURVE  OF  THE  BIG  TREES. 


151 


been  considered.  The  diagrams  shown  in  figures  35,  36,  and  37,  together  with  tables 
A,  B,  and  G,  on  pages  301  and  323,  demonstrate  how  these  factors  have  been  obtained  and 
applied  in  the  case  of  the  sequoia.  Little  need  be  said  of  them  except  to  call  attention  to 
one  or  two  peculiarities.  It  will  be  seen  that  in  figure  35,  showing  the  average  rate  of  growth 
by  centuries,  the  curve  is  very  regular  from  600  to  1800,  but  that  after  that,  when  the  trees 
begin  to  be  old,  it  rises.  This  may  imply  that,  whereas  trees  which  are  to  live  to  great  age 
grow  slowly  during  their  youth,  when  they  get  to  old  age  they  grow  rapidly.  Possibly  this 
is  because  when  the  trees  reach  the  ordinary  age-hmit  of  the  species  most  of  the  individuals 
which  had  been  growing  with  them  die,  and  only  the  few  old  specimens  are  left.  It  is  the 
habit  of  the  sequoia  to  grow  in  groups,  oftentimes  half  a  dozen  trees  of  the  same  age  forming 
a  circle.  Frequently  a  tract  of  many  acres  is  covered  with  trees  of  practically  the  same 
age.  While  a  large  number  of  them  are  alive,  they  naturally  hinder  one  another’s  growth, 
but  when  most  of  them  attain  an  age  of  1,700  or  1,800  years — their  three  score  and  ten — the 
majority  die.  Then  the  few  that  are  left  have  all  the  sun  and  soil  and  rainfall,  and  may 
be  expected  to  grow  more  rapidly  than  ever  before,  or,  at  least,  more  rapidly  in  proportion 
to  their  age.  It  is  possible,  however,  that  a  part  of  the  apparent  increased  growth  of  old 
trees  may  be  due  to  another  cause,  which  will  be  discussed  when  we  come  to  take  up  the 
correction  for  flare  and  for  buttresses. 


Age  of  trees  in  years 

Fig.  36. — Sequoia  washingtoniana :  Corrective  Factor  for  Age,  plotted  by  Centuries. 

(See  Table  A,  p.  301.) 

The  other  of  the  two  main  corrective  factors,  that  for  longevity,  can  not  be  obtained 
without  a  large  number  of  trees.  The  450  sequoias  available  serve  to  make  it  fairly  accu¬ 
rate,  but  not  wholly  so,  for  in  the  corrected  curve  shown  in  figure  38  the  early  parts  have  been 
depressed  too  much.  The  growth  of  the  various  groups  of  sequoias  for  different  periods  of 
their  lives  is  shown  in  figure  37,  and  it  is  evident  that  the  older  trees  in  their  youth,  and  to  a 
less  extent  in  their  maturity,  grow  decidedly  less  rapidly  than  do  those  which  do  not  five 
so  long.  From  the  five  curves  given  in  the  upper  part  of  figure  37  it  would  perhaps  be 
possible  to  deduce  corrective  factors  applicable  to  each  group  and  to  each  decade  of  the  life 
of  each  group.  This  would  involve  so  much  risk  of  error,  however,  that  I  have  not  done  it. 
Instead  I  have  obtained  the  average  growth  of  each  group  during  the  first  1,000  years  of 
its  life  (provided,  of  course,  it  lived  so  long)  and  have  plotted  this  in  the  broken  line  at  the 
bottom  of  figure  37.  Through  this  has  been  drawn  a  smooth  solid  line  which  I  have  used 
as  the  basis  for  the  corrective  factor  for  longevity  as  given  in  Table  B,  page  301.  No 
correction  is  applied  to  the  nine  youngest  groups,  and  a  single  factor  is  used  for  all  of  the  six 
oldest  groups.  To  this  is  probably  due  the  fact  that  the  early  parts  of  the  curve  of  figure  38 
fall  unduly  low.  As  has  been  already  indicated,  the  purpose  of  the  main  corrections,  except¬ 
ing  that  for  absence  of  rings,  is  to  reduce  the  curve  of  tree  growth  as  nearly  as  possible  to  a 


152 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


straight  line  by  eliminating  all  effects  except  those  of  climate.  This  process  has  been 
carried  so  far,  especially  by  the  corrections  for  age  and  longevity,  that  we  have  apparently 
eliminated  and  even  reversed  certain  differences  between  the  remote  past  and  the  present 
which  are  really  due  to  a  difference  in  climate.  The  reader  can  not  be  too  strongly  re¬ 
minded  of  this  fact.  The  curves  of  tree  growth  as  here  presented  show  with  great  exact¬ 
ness  the  cycles  which  are  of  less  duration  than  the  periods  covered  by  the  curve;  but  they 
do  not  show  the  possible  differences  that  may  exist  between  the  mean  climate  of  the  present 
and  of  3,000  years  ago. 


1  2  3  4  5  6  7  8  9  11  13  15  17  19  21  23  25  27  29  31 


No.  of  group 


per  decade  in  mm. 

25.00 


20.00 


15.00 


10.00 


5.00 


0.00 


15.00 


10.00 


/  , 

A 

' 

»  \ 

k 

\ 

> 

!  \ 

/ 

v' 

\ 

\ 

7  Fin 

. 

... 

5.00 

0 

Growth  during  first  250 
years  of  life  of  trees. 


Growth  between  250 
and  650  years  of  age. 


Growth  between  650 
and  1050  years  of  age. 
Growth  between  1050 
and  1450  years  of  age. 

Growth  between  1450 
and  1850  years  of  age. 


Growth  during  first 
1050  years  of  age. 


Fig.  37. — Sequoia  washingtoniana :  Corrective  Factor  for  Longevity. 
(See  Table  B,  p.  301.) 


An  examination  of  the  curve  of  the  sequoias  corrected  for  age  and  longevity,  the  solid 
line  of  figure  38,  shows  that  as  a  whole  it  rises  from  left  to  right  in  a  quite  unexpected  fashion, 
especially  in  the  later  or  right-hand  portions.  Just  where  the  most  marked  rise  begins 
it  is  hard  to  say,  but  from  about  1200  a.  d.  onwards  it  is  plainly  visible,  and  from  1500  a.  d. 
onward  it  is  highly  marked.  This  rise  in  the  curve  seems  at  first  sight  to  indicate  that 
the  climate  of  California  has  been  growing  distinctly  moister  during  the  past  600  or  700 
years,  which  would  be  most  interesting  and  important  if  it  should  prove  to  be  a  fact. 
Yet  other  evidence  points  in  the  contrary  direction.  In  the  first  place,  the  major  changes 
in  California,  as  distinguished  from  the  minor  ones,  appear  on  the  whole  to  agree  with 
those  in  New  Mexico  and  Arizona,  and  in  that  region  there  are  strong  indications  of  greater 
aridity  at  present  than  during  long  periods  in  the  past.  In  California  itself  there  is  not 
much  evidence  on  this  point.  Yet  the  distribution  of  young  sequoias  is  too  important  a 
matter  to  be  overlooked.  In  three  different  localities,  during  the  summers  of  1911  and 
1912,  we  investigated  the  number  of  young  sequoias  as  compared  with  old,  and  as  com¬ 
pared  with  the  number  of  young  trees  of  other  species.  We  found  that  young  trees  are 
abundant  in  moist  places,  such  as  valley  bottoms,  the  flat  tops  of  ridges,  and  hollows 


THE  CURVE  OF  THE  BIG  TREES. 


153 


where  moisture  accumulates  at  certain  times  or  where  it  runs  slowly  through  deep  soil; 
their  number,  however,  is  never  so  great  as  is  the  case  with  other  trees,  such  as  pines, 
firs,  and  cedars,  but  this  is  natural,  since  a  tree  whose  span  of  Hfe  is  so  long  as  that  of  the 
sequoia  does  not  need  to  reproduce  itself  rapidly.  The  number  of  young  trees  is  quite 
sufficient  to  prevent  the  extinction  of  the  species  and  to  insure  that  1,000  or  more  years 
from  now  these  moist  places  shall  have  as  many  sequoias  as  they  have  to-day.  (See  Plate 
5,  page  139.) 

On  dry  slopes,  however,  the  case  is  quite  different.  In  some  places  we  searched  and 
searched,  in  the  hope  of  finding  young  trees.  There  were  plenty  of  mature  ones,  500  or 
1,000  years  old  or  more,  but  practically  no  little  ones.  Now  and  then  a  seedling  or  a 
young  tree  3  or  4  years  old  was  found,  and  once  in  a  while  we  came  upon  large  groups  of 
these  which  had  just  sprung  up.  Between  this  age,  however,  and  an  age  of  many  hundred 
years,  it  was  almost  impossible  to  find  a  tree.  Young  trees  of  other  species  abounded 
wherever  an  old  tree  had  died  and  given  an  opportunity,  and  there  were  pines,  cedars,  and 
firs  of  every  age,  from  seedhngs  to  those  that  were  dying  of  senility.  Actual  count  showed 
that  the  number  of  young  trees  was  many  times  in  excess  of  that  of  old  ones,  and  that  the 


Fig.  38.— Curve  of  Growth  of  the  Sequoia  wasliingtoniana  in  California.  Uncorrected  (...)  and  Corrected  ( - ). 

(See  Table  E,  pp.  308-310.) 


number  decreased  gradually  in  proportion  to  the  age.  With  the  sequoia,  however,  no 
such  thing  was  true.  Often  the  number  of  young  trees  was  actually  much  less  than  that 
of  old  ones.  If  the  trees  in  the  future  reproduce  themselves  no  faster  than  they  have 
during  the  past  500  years  or  more,  the  species  will  ultimately  become  extinct  upon  these 
slopes.  Seeds  are  apparently  able  to  sprout  during  moist  years,  and  to  grow  as  long  as 
the  rainfall  continues  propitious,  but  as  soon  as  dry  years  come  the  httle  trees  die.  Thus 
the  sequoia  in  the  dry  parts  of  the  forest  has  not  been  able  to  reproduce  itself,  although 
in  the  moist  parts  it  holds  its  own.  Apparently  the  average  conditions  extending  over 
centuries  can  not  be  the  same  now  as  in  the  past.  If  they  were,  young  sequoias  ought  to 
be  abundant.  The  only  explanation  of  the  absence  of  young  trees  seems  to  be  a  change 
from  the  past  to  the  present. 

In  the  face  of  this  stands  the  curve  of  figure  38,  as  it  appears  after  the  corrections 
for  age  and  longevity  have  been  apphed.  At  the  end  of  our  first  season’s  work,  when 
the  curve  for  the  trees  measured  that  year  was  plotted,  I  confess  that  I  was  greatly  puzzled. 
The  evidence  of  the  curve  seemed  too  strong  to  admit  of  doubt ;  but  at  the  same  time  the 
absence  of  young  trees  on  the  dry  slopes  where  the  old  ones  flourished,  together  with  the 
abundant  evidences  of  desiccation  in  other  parts  of  the  world,  also  seemed  too  strong  to 
doubt.  On  returning  to  the  Sierras  a  second  time,  however,  in  1912,  the  difficulty  soon 
solved  itself.  Two  things  have  a  share  in  causing  the  growth  of  recent  centuries  to  appear 
greater  than  it  really  is.  One  of  these  is  the  form  of  the  trunk  of  the  sequoia,  and  the  other 
our  choice  of  places  for  measurement.  The  sequoia  habitually  grows  with  a  round,  smooth 


154 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


trunk  which  maintains  its  thickness  well  up  to  the  top,  so  that  for  long  distances  the 
diameter  varies  only  at  a  very  slow  rate.  At  the  base,  however,  as  soon  as  the  trees  become 
of  any  considerable  age,  the  trunks  flare  and  send  out  buttresses.  The  woodsmen  who 
fell  the  trees  naturally  prefer  to  do  their  cutting  at  a  point  above  the  flaring  portion,  and 
thus  save  themselves  the  work  of  cutting  through  the  extra  thickness.  In  the  case  of 
young  trees,  not  over  1,000  years  of  age,  this  is  feasible,  although  it  necessitates  the  building 
of  a  platform  at  a  height  of  6  feet  or  so  above  the  ground.  In  the  case  of  older  trees  the 
amount  of  flaring  is  so  great  that  it  is  impracticable  to  avoid  it  unless  the  trees  are  cut  at 
a  height  of  15  or  20  feet.  When  the  lumbering  of  the  sequoias  was  first  begun,  this  was 
sometimes  done,  and  in  order  to  climb  to  the  top  of  certain  old  stumps  we  were  obliged  to 
throw  ropes  over  them  and  clamber  to  the  height  of  a  second-story  window. 

In  later  years,  however,  the  practise  has  been  to  cut  the  trees  low.  Some  of  the  best 
and  oldest  stumps  are  cut  not  more  than  3  or  4  feet  from  the  ground,  and  5  or  6  feet  is 
the  ordinary  height.  In  the  flaring  portion  of  a  trunk  the  arrangement  of  the  rings,  as  it 
appears  in  a  vertical  section  through  the  middle,  is  illustrated  in  figure  39,  where  it  will 
be  seen  that  the  central  rings — those  which 
grew  while  the  tree  was  young — are  vertical 
and  the  Hne  of  cutting  is  at  right  angles  to  them; 
but  the  later  rings  have  a  distinct  slope  parallel 
to  the  flare  of  the  tree.  Hence,  when  they  are 
cut  horizontally  by  the  saw  of  the  woodsman,  as 
indicated  by  the  sohd  hne  AB,  they  are  not  tran¬ 
sected  at  right  angles.  Thus  their  apparent 
width,  as  seen  on  the  surface  of  the  stump,  is 
greater  than  their  real  width,  as  shown  in  the 
dotted  lines.  In  a  few  special  cases  we  were 
able  to  make  allowances  for  this  and  to  measure 
the  rings  at  right  angles  instead  of  horizontally; 
but  in  the  majority  of  cases  this  was  utterly  out 
of  the  question.  It  would  have  involved  so 
much  cutting,  so  much  extra  time  in  measuring,  and  so  much  danger  of  making  mistakes 
in  counting  and  measuring,  that  not  only  would  the  number  of  trees  that  we  could  measure 
have  been  too  small  to  give  reliable  results,  but  the  character  of  the  measurements  would 
have  been  more  open  to  question  than  is  now  the  case.  The  only  course  seemed  to  be  to 
measure  horizontally  and  then  to  make  corrections  in  the  final  curve. 

The  degree  to  which  this  flare  at  the  base  of  the  trunk  is  effective  may  be  judged  some¬ 
what  from  table  6.  This  table  is  compiled  from  sections  of  wood  cut  from  relatively  young 
trees,  for  the  purpose  of  making  measurements  of  the  growth  during  the  last  50  or  100 
years,  by  years  instead  of  by  decades.  Trees  having  a  diameter  of  not  over  6  or  7  feet 
near  the  base  and  not  over  600  or  1,000  years  old  were  selected;  yet  even  these  relatively 
young  trees  flare  considerably.  Out  of  85  specimens  which  happen  to  be  at  hand  at  the 
time  of  writing,  I  have  selected  the  32  which  show  this  effect  most  clearly.  A  glance  at 
the  table  shows  that  the  horizontal  distance  along  which  measurements  are  made  exceeds 
the  actual  distance  at  right  angles  to  the  rings  by  amounts  varying  from  3  per  cent  to  16 
per  cent,  the  average  being  7.6  per  cent.  Out  of  the  85  trees,  32  others,  while  flaring 
noticeably,  show  a  less  degree  of  flaring — that  is,  2  to  5  per  cent — ^while  21  show  the  effect 
of  flaring  to  the  extent  of  2  per  cent  or  less,  and  may  be  considered  practically  straight.  If 
the  curve  of  growth  of  the  32  young  trees  whose  flare  has  been  calculated  were  plotted 
without  further  correction,  the  part  belonging  to  the  present  time  would  be  nearly  8  per 
cent  too  high  in  comparison  with  the  earlier  parts.  With  old  trees  this  effect  is  exaggerated. 
From  this  in  part  comes  the  rise  in  the  latter  part  of  the  sohd  hne  in  figure  38. 


Fig.  39. — Effect  of  Flaring  Buttresses  on  the 
Measurementof  Rings  of  Growth. 


THE  CURVE  OF  THE  BIG  TREES. 


155 


Table  6. — Effect  of  flare  at  base  of  sequoias. 


Field  No. 
of  tree. 

No.  of  years 
available  for 
measure¬ 
ment. 

Horizontal 
measurement 
of  section  in 
mm.  =  A. 

True  thick¬ 
ness  of  sec¬ 
tion  when 
measured  at 
right  angles 
to  the  rings 
=  B. 

Ratio  of 
A/B. 

Field  No. 
of  tree. 

No.  of  years 
available  for 
measure¬ 
ment. 

Horizontal 
measurement 
of  section  in 
mm.  =  A. 

True  thick¬ 
ness  of  sec¬ 
tion  when 
measured  at 
right  angles 
to  the  rings 
=  B. 

Ratio  of 
A/B. 

2003 

64 

83 

73 

1.13 

3059 

20 

94 

86 

1.09 

2007 

64 

99 

94 

1.05 

3061 

52 

219 

211 

1.04 

2014 

7 

186 

174 

1.07 

3063 

74 

143 

136 

1.05 

2016 

105 

126 

114 

1.10 

3065 

7 

125 

116 

1.08 

2021 

74 

175 

166 

1.05 

3050 

84 

131 

126 

1.04 

2029 

99 

165 

152 

1.08 

3062 

72 

146 

131 

1.11 

X 

63 

130 

114 

1.14 

3069 

86 

122 

116 

1.05 

3030 

67 

174 

150 

1.16 

3077 

71 

173 

159 

1.09 

3031 

63 

168 

157 

1.07 

3078 

62 

123 

119 

1.03 

3032 

84 

232 

209 

1.11 

3080 

63 

112 

105 

1.07 

3034 

94 

227 

205 

1.11 

3085 

71 

142 

133 

1.07 

3035 

47 

195 

181 

1.08 

3082 

114 

142 

137 

1.04 

3042 

102 

130 

124 

1.05 

3087 

50 

179 

168 

1.06 

3046 

66 

165 

158 

1.04 

3091 

63 

192 

185 

1.04 

3054 

31 

140 

128 

1.09 

3090 

54 

177 

165 

1.07 

3055 

26 

171 

153 

1.12 

3057 

28 

200 

190 

1.05 

Total . 

1983 

.... 

.... 

34.43 

Average. . . 

64 

.... 

1.076 

Still  another  factor  produces  an  error  in  this  same  direction.  As  the  trees  get  older 
they  tend  to  throw  out  buttresses  at  the  base.  In  the  center  of  the  buttresses  the  rings 
of  growth  are  well  developed,  wide,  easily  measured  and  counted,  and  are  rarely  missing. 
In  the  portions  between  the  buttresses  they  are  thinner,  more  crinkled  and  hence  hard 
to  measure,  and  are  more  apt  to  be  missing  than  in  the  neighboring  buttresses.  When 
the  tree  is  younger  and  there  are  no  buttresses,  the  rings  preserve  nearly  the  same  width 
throughout  the  entire  circumference,  and  a  measurement  in  one  place  is  as  good  as  in 
another.  Where  the  buttresses  exist,  however,  a  measurement  along  them  gives  an 
impression  of  growth  greater  than  is  warranted  by  the  facts.  If  the  buttresses  and  the 
depressions  between  them  are  averaged  together,  the  average  growth  of  an  old  tree  appears 
to  be  distinctly  less  than  where  the  buttresses  alone  are  measured.  It  would  be  possible 
to  avoid  a  part  of  the  error  due  to  buttresses  by  choosing  only  young  or  uncommonly 
symmetrical  trees  which  flare  but  little.  We  were  confronted,  however,  by  the  paramount 
necessity  of  finding  as  many  old  trees  as  possible;  therefore  we  felt  obliged  to  take  every 
tree  of  great  size  which  gave  promise  of  giving  fairly  accurate  measurements.  The  errors 
involved  in  measuring  along  the  buttresses  are  less  serious  than  those  which  would  have 
arisen  had  we  measured  along  the  hollows,  where  there  was  danger  of  losing  a  considerable 
number  of  rings.  After  the  danger  of  the  buttresses  was  realized,  we  tried,  so  far  as 
possible,  to  take  our  measurements  from  points  half-way  between  buttress  and  hollow, 
but  this  in  many  cases  proved  impracticable,  and  we  were  thrown  back  upon  the  good,  clean 
sections  of  the  buttresses. 

From  what  has  been  said  above,  it  is  evident  that  the  corrected  curve  of  growth  of 
the  sequoias,  as  given  in  figure  38,  is  wrong  in  two  respects:  (1)  the  early  portions  fall 
unduly  low,  partly  because  of  scarcity  of  data  and  consequent  imperfections  in  the  cor¬ 
rection  for  age  and  longevity,  and  partly  because  those  corrections  are  deliberately  designed 
to  eliminate  any  effects  due  to  a  change  of  climate  occurring  in  a  cycle  of  3,000  years  or 
more;  (2)  the  later  part  of  the  curve  rises  too  high  on  account  of  the  flaring  buttresses 
at  the  base  of  the  trunks  of  the  trees.  With  our  present  incomplete  data  these  two  errors 
can  not  be  eliminated  by  any  strictly  mathematical  correction.  The  best  that  we  can  do  is 
to  adopt  some  standard  unconnected  mth  the  trees,  and  swing  the  curve  of  growth  so 
that  at  a  few  critical  points  the  relative  height  of  the  two  is  the  same,  taking  the  greatest 
care,  however,  that  we  do  not  alter  the  sinuosities.  For  this  purpose  I  have  adopted  the 
fluctuations  of  the  Caspian  Sea  as  given  in  Chapter  XVII  of  the  “The  Pulse  of  Asia.” 


156 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


This  involves  anticipation  of  two  conclusions  which  are  to  be  discussed  in  the  following 
chapter;  first,  that  the  sinuosities  of  the  sequoia  curve  actually  represent  pulsations  be¬ 
tween  aridity  and  moisture;  second,  that  the  pulsations  in  California  have  been  essentially 
synchronous  with  those  of  Central  Asia. 

Assuming  for  the  present  that  these  two  conclusions  are  valid,  we  may  correct  the 
curve  of  the  sequoia.  For  this  purpose,  the  following  critical  levels  of  the  Caspian  Sea 
have  been  taken  as  the  standard : 

Mean  level  1750-1890  a.  d.  equals  0  feet. 

Recorded  high  level  in  920  a.  d.  equals  +29  feet. 

Estimated  level  below  ruins  now  under  water,  in  seventh  century,  —20  feet. 

Estimated  level  about  the  time  of  Christ  +85  feet. 

Estimated  level  about  the  time  of  Herodotus  +150  feet. 

The  historic  and  physiographic  evidence  in  support  of  these  figures  is  given  in  the 
chapter  of  “The  Pulse  of  Asia”  already  referred  to.  On  the  basis  of  these  levels  of  the 
Caspian  Sea  the  curve  of  the  sequoias  has  been  tilted  in  such  a  way  that  the  portions  at 
the  respective  dates  given  above  he  at  heights  approximately  proportional  to  the  height  of 
the  Caspian  Sea  at  the  corresponding  dates.  Further  than  this  no  change  has  been  made. 
In  applying  this  “Caspian  corrective  factor,”  the  sequoia  curve  has  been  divided  into 
four  portions:  (1)  from  the  earliest  times  until  400  b.  c.,  a  portion  which  has  simply  been 
raised  to  correspond  with  the  inferred  level  of  the  Caspian  at  400  b.  c.  but  has  not  been 
tilted  because  we  have  no  knowledge  of  the  sea  in  earlier  times;  (2)  400  b.  c.  to  400  a.  d., 
which  has  been  tilted  in  such  a  way  that  400  b.  c.  hes  15  per  cent  higher  than  in  the  curve 
of  figure  38,  while  400  a.  d.  is  unchanged;  (3)  400  a.  d.  to  900  a.  d.,  which  is  unchanged, 
and  (4)  900  a.  n.  to  the  present  time,  which  has  been  tilted  so  that  the  modern  end  of  the 
curve  hes  9  per  cent  lower  than  in  figure  38.  In  addition  to  this  I  have  arbitrarily  made  a 
slight  reduction  in  the  great  maximum  which  culminates  about  1000  b.  c.,  but  this  is  a 
matter  of  no  importance.  The  exact  extent  to  which  the  position  of  the  curve  has  been 
altered  in  each  decade  is  indicated  in  the  column  headed  “Caspian  Corrective  Factor” 
in  Table  G,  pages  323-324. 

The  resultant  curve,  given  in  figure  50  on  page  172,  represents  the  nearest  approxi¬ 
mation  that  now  seems  possible  to  the  actual  curve  of  growth  of  the  sequoias  as  it  would 
be  if  it  were  uninfluenced  by  differences  in  the  rate  of  growth  of  old  trees  and  young,  or 
by  any  other  influences  except  those  of  climate.  Its  further  discussion  will  be  deferred 
until  we  have  considered  the  reasons  for  beheving  that  the  low  portions  indicate  aridity, 
while  the  high  indicate  abundant  moisture ;  but  one  vital  point  must  again  be  emphasized : 
it  may  seem,  perhaps,  that  we  have  taken  liberties  with  our  curve  of  growth  and  have 
altered  it  arbitrarily;  but  this  is  far  from  the  case.  Every  alteration  has  been  based  on 
strictly  mathematical  considerations,  and  no  assumptions  have  been  made  except  at  the 
very  end,  where  the  Caspian  factor  is  used.  Even  so,  nothing  has  been  done  to  alter  the 
location  of  the  sinuosities  of  the  curve.  A  comparison  of  the  dotted  hne  of  figure  38  and 
the  sohd  line  of  figure  50  shows  that  although  many  corrections  have  been  apphed,  the 
essential  features,  that  is,  the  ups  and  downs  which  appear  to  indicate  chmatic  pulsations, 
have  not  been  essentially  changed  either  in  position  or  in  relative  importance. 


CHAPTER  XIV. 

THE  INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 

The  rate  of  growth  of  the  vegetation  in  any  given  locality  varies  from  year  to  year, 
chiefly  because  of  changes  in  precipitation  and  temperature.  In  northern  regions,  where 
there  is  precipitation  at  all  seasons,  temperature  is  probably  the  most  important  factor. 
Farther  south,  however,  the  amount  of  rain  becomes  of  increasing  importance.  Professor 
Douglass  has  shown,  as  we  have  seen,  that,  in  spite  of  all  the  accidents  to  which  plants 
are  liable,  three  or  four  yellow  pines  are  sufficient  to  give  a  record  of  the  rainfall  in  Arizona 
with  an  accuracy  of  approximately  70  per  cent.  This  is  true  even  where  individual  years 
are  concerned.  If  we  employ  a  unit  of  time  longer  than  a  single  year,  so  that  the  stored-up 
moisture  of  the  soil  and  energy  of  the  tree  have  less  effect,  and  if  we  base  our  conclusions  on 
a  large  number  of  trees  instead  of  a  few,  the  agreement  between  rainfall  and  growth  must 
become  much  greater  than  70  per  cent.  It  would  seem,  indeed,  that  with  a  time-unit 
of  10  years  and  with  a  number  of  trees  amounting  to  hundreds  the  agreement  ought  to 
be  over  90  per  cent.  This  conclusion,  however,  is  based  solely  on  the  yellow  pine  of 
Arizona.  Before  it  can  be  applied  to  other  species  in  other  parts  of  the  country,  further 
investigation  is  necessary.  In  the  Sierras,  where  the  sequoias  grow,  the  climatic  conditions 
are  in  many  ways  similar  to  those  of  the  high  plateaus  of  Arizona,  where  the  yellow  pines 
have  their  habitat.  The  total  precipitation  in  the  sequoia  region,  however,  is  much  greater 
than  among  the  pines,  perhaps  twice  as  much.  Moreover,  there  are  no  summer  rains  in 
California,  which  adds  another  element  of  difference.  Yet  in  spite  of  the  differences  the 
two  regions  are  sufficiently  alike  to  cause  us  to  infer  that  in  both  places  trees  of  the  same 
species  would  be  similarly  influenced  by  variations  of  rainfall.  The  introduction  of  a 
new  species,  however,  may  completely  reverse  matters.  Hence  we  are  not  justified  in 
drawing  any  conclusions  as  to  the  sequoia  until  we  have  made  a  comparison  of  actual 
measurements  of  the  growth  of  the  trees  year  by  year  with  the  precipitation  at  the  nearest 
possible  meteorological  stations. 

The  rainfall  of  central  California — that  is,  of  the  portion  of  the  State  Ijdng  west  of  the 
Sierra  Mountains  between  latitudes  35°  and  39° — varies  enormously.  In  the  southern  part 
of  the  Great  Valley  near  Bakersfield  and  the  Kern  Lakes  it  averages  only  5  to  10  inches  a 
year,  and  in  no  part  of  the  valley  does  it  rise  much  above  15  inches  on  an  average,  though  in 
individual  years  it  rises  twice  as  high.  In  the  Sierras  at  an  altitude  of  4,000  feet  or  more,  and 
in  the  Coast  Range  at  somewhat  lower  altitudes,  it  rises  in  some  places  to  an  average  of 
50  to  60  inches  per  year.  In  spite  of  this  difference  in  amount,  however,  the  proportional 
variations  from  year  to  year  in  different  places  are  closely  similar.  This  is  evident  from 
an  inspection  of  figure  40,  which  represents  the  annual  rainfall  since  records  began  to  be 
kept  at  selected  meteorological  stations  in  various  parts  of  central  California.  In  view  of 
the  long,  dry  season  in  summer  the  precipitation  is  naturally  reckoned  from  July  to  July 
rather  than  from  January  to  January.  The  first  curve  represents  the  rainfall  at  Fresno. 
This  is  placed  first  because  it  is  the  one  chiefly  employed  for  comparison  with  the  tree 
curves.  The  next  curve  shows  the  rainfall  at  Bakersfield,  which  hes  in  the  southern  part 
of  the  Great  Valley  and  is  selected  partly  because  it  lies  well  to  the  south  and  partly  because, 
with  an  average  rainfall  of  only  about  5  inches,  it  is  the  driest  place  in  the  whole  district. 
The  next  two  curves  represent  Portersville  and  Tulare,  which  lie  in  the  Great  Valley,  not 
far  from  the  base  of  the  Sierras,  and  have  been  selected  because,  being  about  35  and  50 

157 


158 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


miles  from  Dillonwood,  they  are  the  nearest  records  of  any  considerable  length  available 
for  comparison  with  the  growth  of  the  sequoias  at  that  place.  The  next  curve  is  that 
of  Sanger,  the  meteorological  station  nearest  to  Hume,  where  most  of  our  sequoias  grew.  If 
we  continue  to  mention  the  curves  in  the  order  of  geographical  location,  the  next  should 
be  the  one  for  Fresno,  which  is  here  plotted  at  the  top.  Since  the  record  for  Fresno  goes 
back  to  1881-82  while  that  for  Sanger  goes  only  to  1889-90,  and  since  Fresno  is  only  a  little 
more  distant  from  Hume  than  is  Sanger,  Fresno  has  been  chosen  for  comparison  with  the 


1850  Pate 


1800 


1870 


1880 


1890 


1900 


1910 


Fresno, altitude 
A  293  ft.  mean 
rainfall  10.02  in. 


Bakersfield 
B  altitude  394  ft. 
mean  rainfall  5.17  in. 


Porterville. 
•i&l'-C  altitude  464  ft. 

mean  rainfall  10.01  In. 
Tulare.altitude 
D  274  ft.  mean 
rainfall  8.87  in* 
Sanger,  Fresno  Co. 

E  altitude  871  ft. 
mean  rainfall  10.68  in. 

20 

Stock  ton, altitude 
F  23  ft.,  mean 
rainfall  14.63  in. 


San  Francisco, 

G  altitude  207  ft. ,  mean 
rainfall  22.83  in. 

25 

Mean  of  Monterey, 

>  H  Stockton,  Santa  Barbara. 

and  Sfui  Francisco 
56l 


Mokelumne  Hill. 
Calaveias  Co.,  alt. 
1550  ft.,  mean 
rainfall  32.52  in. 


Milo,  Tulare  Co., 

J  altitude  1600  ft.,  mean 
rainfall  23.84  in. 


Crockers, 
Tuolumne  (^., 
K  altitude  ^26  ft. 
mean  rainfall 
49.47  in. 


Fig.  40. — Annual  Rainfall  at  Selected  Stations  in  California. 


growth  of  the  trees  at  Hume.  Northwest  of  Fresno,  at  a  distance  of  120  miles,  Stockton 
lies  in  the  Great  Valley  on  the  way  to  San  Francisco.  Its  curve  of  precipitation  goes  back 
to  1867-68.  It  is  chiefly  important  as  a  meteorological  way-station  between  the  sequoias 
and  San  Francisco.  The  next  curve  and  all  those  below  it  are  extremely  jagged;  for, 
although  the  rainfall  of  the  places  represented  in  the  later  curves  ranges  from  20  to  55 


INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


159 


inches,  instead  of  from  5  to  20  as  in  the  preceding  places,  the  same  scale  is  employed  for 
purposes  of  comparison.  The  curve  for  San  Francisco  is  the  most  important,  since  it 
goes  back  with  a  good  degree  of  accuracy  to  1849-50.  Below  the  San  Francisco  curve 
comes  a  closely  similar  one,  showing  the  average  rainfall  for  San  Francisco  itself,  together 
with  Stockton  to  the  east  of  it  in  the  Great  Valley,  and  Monterey  and  Santa  Barbara,  which 
lie  respectively  100  miles  and  275  miles  down  the  coast  from  San  Francisco.  These  four 
places  were  selected  simply  because  they  possess  meteorological  records  going  back  farther 
than  those  of  any  other  towns  in  this  region.  Among  the  last  three  curves,  the  one  for 
Milo,  at  an  altitude  of  1,600  feet  in  Tulare  County,  between  Portersville  and  Dillonwood,  has 
been  selected  not  only  because  it  is  a  mountain  station,  but  because  it  is  the  nearest  to 
Dillonwood.  Unfortunately  this  record  is  very  short.  The  other  two  curves,  for  Moke- 
lumne  Hill,  at  an  altitude  of  1,550  feet  in  Calaveras  County,  and  for  Crocker’s,  at  an  altitude 
of  4,450  feet  in  Tuolumne  County,  have  been  selected  because,  although  these  two  places 
are  respectively  100  and  150  miles  northwest  of  Hume,  they  are  almost  the  only  available 
examples  of  the  abundant  precipitation  which  characterizes  the  mountainous  regions  in  the 
vicinity  of  the  great  sequoia  groves.  All  of  them  lie  lower  and  have  probably  less  rainfall 
than  the  habitat  of  the  sequoias,  but  the  conditions  at  Crocker’s  appear  to  be  closely  similar 
to  those  where  most  of  the  Big  Trees  are  found. 

Inspection  of  the  eleven  curves  of  annual  rainfall  in  figure  40  shows  that  they  agree 
closely  as  to  their  main  featmes.  The  years  1868,  1872, 1874, 1876, 1878,  1884,  1886, 1890, 
and  1895  show  maxima  in  every  curve.  The  maximum  of  1897  appears  in  all  the  curves 
except  that  for  Stockton  and  that  for  1901  in  all  except  Bakersfield.  Either  1880  or  1881 
shows  a  maximum  in  every  case,  and  both  years  are  always  above  the  average.  Finally, 
either  1906  or  1907  shows  a  maximum  in  each  curve.  The  minima  agree  quite  as  markedly 
as  the  maxima.  In  fact  the  annual  distribution  of  rainfall  in  any  of  the  less  extreme  places 
in  central  California  may  be  taken  as  typical  of  the  whole  region.  Thus  a  long  record,  such 
as  that  of  San  Francisco,  may  be  used  to  give  an  approximate  record  for  any  other  place, 
simply  by  multiplying  the  San  Francisco  values  by  a  sum  sufficient  to  change  the  mean 
value  of  the  San  Francisco  record  to  the  mean  value  of  the  other  record  for  the  same  period 
of  time.  This  process  of  “making  up”  records  is  in  common  use  among  meteorologists. 

I  am  indebted  to  Professor  Alexander  G.  McAdie,  of  the  local  Weather  Bureau  at  San 
Francisco,  for  having  made  up  a  record  for  Fresno  by  comparison  with  San  Francisco. 
The  factor  in  this  case  is  0.47.  In  the  comparisons  of  rainfall  and  tree  growth  that  follow 
I  have  used  this  made-up  record  for  Fresno  for  the  period  from  1850  to  1882,  and  the 
actual  record  from  1882  onward.  I  shall  not  refer  to  this  matter  again,  but  shall  simply 
treat  the  combined  made-up  and  actual  records  as  if  they  were  of  equal  value.  The 
agreement  between  variations  in  rainfall  from  place  to  place  applies  not  merely  to  the 
annual  rainfall  but  also  to  that  by  months,  although  not  to  so  great  an  extent.  This  is 
evident  from  figure  41,  where  the  monthly  distribution  of  precipitation  for  the  8  years 
beginning  with  1889-90  and  ending  with  1896-97  has  been  plotted  for  Portersville,  Fresno, 
and  San  Francisco.  Inasmuch  as  the  rainfall  of  San  Francisco  is  more  than  double  that 
of  the  other  two  places,  it  has  been  plotted  on  half  as  large  a  scale.  Apart  from  what  may 
be  called  accidental  details,  the  general  form  of  the  three  curves  is  similar,  and  the  three 
curves  for  any  one  year  resemble  one  another  more  than  do  the  curves  for  any  given  place 
for  three  successive  years.  On  the  basis  of  the  agreement  here  shown,  it  seems  permis¬ 
sible  to  use  the  San  Francisco  record  as  the  basis  for  a  made-up  record  of  monthly  as  well  as 
annual  rainfall  for  Fresno  prior  to  1882.  I  shall  do  this  when  we  come  to  a  discussion  of 
the  type  of  seasonal  distribution  of  precipitation  which  most  stimulates  the  growth  of  trees. 

The  actual  comparison  of  the  rate  of  growth  of  trees  with  the  precipitation  for  the 
season  beginning  in  July  of  the  preceding  year  and  ending  in  July  of  the  year  of  growth  is 
at  first  sight  inconclusive  and  puzzling.  Let  us  examine  the  matter  in  two  separate  cases. 


160 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


The  first  is  shown  in  figm’e  42,  where  the  precipitation  at  Porterville  is  compared  directly 
with  the  growth  of  young  sequoias  at  Dillonwood  between  30  and  40  miles  to  the  east  of 
Porterville  and  6,000  feet  above  it.  The  measurements  used  in  preparing  the  two  curves 
of  growth  here  shown  consist  of  group  A  (46  measurements  of  19  trees,  none  of  which 
was  over  100  years  of  age  and  most  of  which  were  less  than  40  years  of  age)  and  group 
B  (8  measurements  upon  5  trees  having  an  age  of  from  100  to  150  years).  Several  of  the 


San  Francisco  = 
Fresno  = 

Porterville  •» 


INTERPKETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


161 


older  trees  were  sickly  and  were  cut  by  accident,  that  is,  the  purpose  was  to  cut  young 
trees,  not  over  100  years  of  age,  but  those  of  group  B,  having  grown  slowly,  appeared 
younger  than  they  actually  were.  Hence  their  curve  is  low  and  has  few  variations,  but 
it  agrees  fairly  well  with  that  of  the  younger  trees.  Both  curves  have  maxima  in  1881, 
1885,  1888,  1900,  and  1903,  and  the  maximum  of  1907  in  the  lower  curve  agrees  with  a 
marked  increase  in  growth  in  the  upper  curve  followed  by  a  maximum  the  succeeding  year. 
A  marked  difference  in  the  curves  is  seen  in  1890,  where  the  younger  trees  much  increased 
their  growth  while  the  older  trees  remained  practically  stationary.  This  seems  to  mean  that 
the  very  young  and  rapidly  growing  trees  of  group  B  were  stimulated  by  the  heavy  rains  of 
1889  and  1890,  while  the  older  trees  were  unaffected.  Apparently  the  stimulus  given  to 
the  young  trees  gave  them  such  vigor  that  its  effects  did  not  disappear  for  15  years. 


Fig.  42. — Rainfall  at  Portersville  Compared  ivdth  Growth  of  Sequoias  at  Dillonwood. 

(See  Table  I.  pp.  328-329.) 


When  the  curves  of  growth  are  compared  with  the  curves  of  precipitation  it  appears  at 
once  that  they  do  not  agree  at  all  closely,  nothing  like  so  closely  as  in  the  cases  cited  by 
Professor  Douglass;  yet  on  closer  examination  it  appears  that  there  is  a  certain  amount  of 
agreement,  although  this  is  by  no  means  noticeable.  For  instance,  in  1881,  1890,  and  1897 
the  curve  for  the  larger  number  of  trees — that  is,  group  B — and  the  rainfall  curves  are  both 
at  a  maximum.  In  1895  the  rainfall  curve  reaches  a  maximum,  which  does  not  appear  in  the 
tree  curve,  apparently  because  of  the  very  dry  year  just  preceding.  In  1901  the  rain  is 
again  at  a  maximum,  and  the  tree  curve  is  high,  although  the  maximum  growth  was  attained 
a  year  earher.  In  1905  and  1906  a  marked  disagreement  is  noticed,  for  in  those  years  the 
rainfall  was  uncommonly  heavy,  while  the  trees  grew  uncommonly  slowly.  This  seems  to 
be  due  to  the  fact  that  the  preceding  years  had  been  dry  and  therefore  the  growth  of  the 
trees  had  been  much  checked.  In  1906  the  rain  at  Portersville  and  Tulare  did  not  come  in  ^ 
great  abundance  until  March,  April,  and  May,  during  which  months  over  12  inches  fell  at 
Portersville  instead  of  the  usual  3.25  inches.  Much  of  this,  coming  so  late,  ran  quickly  off, 
yet  part  of  it  was  probably  retained,  and  the  way  thus  prepared  for  the  rapid  growth  of 
the  trees  in  1907. 

12 


162 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Trees,  like  other  living  beings,  possess  much  inertia.  If  they  are  subjected  to  favorable 
conditions  for  a  few  years  and  make  a  good  growth,  they  are  in  a  position  to  keep  on  in 
the  same  way  unless  seriously  checked.  Therefore,  in  estimating  the  effect  which  the 
conditions  of  an  individual  season  have  upon  their  growth,  the  actual  amount  of  growth 
is  less  important  than  the  change  from  preceding  years.  Accordingly  I  have  added  to 
figure  42  a  lower  line  showing  the  differential  growth  of  the  trees  at  Dillonwood — that  is, 
the  amount  of  increase  or  decrease  of  growth  compared  with  the  year  immediately  pre¬ 
ceding.  This  curve  shows  a  fair  degree  of  agreement  with  the  curves  of  precipitation,  but 
there  are  also  disagreements,  such  as  1887  and  1903.  Other  factors  besides  the  rainfall  of 
the  season  immediately  preceding  the  year  of  growth  evidently  have  a  large  effect  upon  the 
trees.  Moreover,  our  records  of  rainfall  are  derived  from  places  30  to  50  miles  from  where  the 
trees  were  located.  Nevertheless,  in  cases  like  1881, 1890, 1897, 1900,  and  1907,  there  seems 
reason  to  think  that  we  can  see  the  direct  effect  of  the  precipitation  of  the  preceding  winters. 
Yet  in  spite  of  this,  these  Dillonwood  curves  might  be  used  almost  as  well  to  show  that 
rainfall  and  tree  growth  do  not  agree  as  to  show  that  they  agree.  They  have  been  intro¬ 
duced  here  purposely  in  order  to  show  the  difficulties,  and  in  order  to  emphasize  certain 
facts  which  will  be  brought  out  later;  namely,  that  the  growth  of  the  trees  depends  upon 
the  rainfall  of  several  years,  and  not  of  one  year,  and  that  it  is  influenced  by  the  season 
at  which  precipitation  falls  quite  as  much  as  by  the  actual  amount  of  precipitation. 


(See  Table  I,  pp.  328-329.) 


It  would  be  possible  to  go  on  and  show  more  clearly  the  exact  nature  and  degree  of  the 
effects  produced  upon  the  Dillonwood  trees  by  past  rainfall  and  by  variations  in  its 
seasonal  occurrence,  but  as  only  a  small  part  of  the  measurements  used  in  our  final 
long  curve  of  growth  (extending  back  over  many  centuries)  came  from  Dillonwood  and  the 
other  regions  near  Portersville,  it  seems  wiser  to  discuss  the  matter  in  relation  to  the  trees 
at  Hume.  At  that  place  I  pursued  a  method  somewhat  different,  and  on  the  whole  distinctly 
more  reliable,  than  that  followed  at  Dillonwood.  Instead  of  cutting  young  trees,  whose 
youth  makes  them  particularly  liable  to  be  affected  by  accidents,  I  selected  over  100  vigor¬ 
ous  trees  in  early  maturity;  they  were  from  5  to  8  feet  in  diameter  and  had  a  probable  age 
of  from  500  to  1,000  years.  The  Hume-Bennett  Lumber  Company,  on  whose  land  they 
stood,  kindly  gave  me  permission  to  cut  from  them  small  sections  8  or  12  inches  in  length 
and  showing  the  rings  of  growth  for  a  period  varying  from  30  to  nearly  200  years.  The 
difference  in  the  number  of  rings  depends  partly  on  the  size  of  the  sections,  but  it  is  far 
more  largely  dependent  on  the  rate  of  growth  of  the  trees,  for  a  slow-growing  tree  of  course 
shows  many  more  rings  per  inch  than  does  a  fast-growing  one.  On  the  basis  of  the  number 
of  rings  the  111  sections  have  been  divided  into  three  groups,  and  the  first  two  groups  have 
each  been  divided  into  two  subgroups,  one  of  which  grew  in  wet,  swampy  places,  and  the 
other  upon  drier  slopes. 


INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


163 


The  groups  are  as  follows: 

Group  I.  Sections  showing  60  rings  or  less;  trees  of  rapid  growth:  (a)  From  dry  local¬ 
ities,  23  sections,  (fe)  From  damp  localities,  14  sections. 

Group  II.  Sections  showing  from  60  to  100  rings;  trees  of  moderate  growth:  (a)  From 
dry  localities,  31  sections,  (b)  From  damp  localities,  18  sections. 

Group  III.  Sections  showing  over  100  rings;  trees  of  slow  growth:  (a)  From  dry  local¬ 
ities,  25  sections.  (6)  From  damp  localities,  no  sections.  (Trees  in  damp  places 
almost  universally  grow  rapidly.) 

The  uncorrected  curves  of  growth  derived  from  these  five  groups  are  shown  in  figure  43. 
The  solid  lines  represent  the  trees  living  in  damp  localities,  while  the  dotted  lines  represent 
those  from  dry  localities.  The  trees  in  the  swamps  grow  the  fastest,  as  would  naturally 
be  expected,  but  in  times  of  adversity  they  appear  to  be  the  first  to  suffer  and  are  on  the 
whole  more  affected  than  are  those  in  the  drier  locations.  Hence  we  conclude  that,  for  a 
curve  of  growth  possessing  the  highest  degree  of  accuracy,  vigorous,  rapidly  growing  trees 
located  in  small  swamps  which  are  easily  dried  up  are  the  most  advantageous.  The  differ¬ 
ence  in  the  form  of  the  various  curves,  however,  is  comparatively  slight,  except  that  the 
rate  of  growth  in  the  successive  groups  is  slower  and  slower.  In  general  the  curves  show 
periods  of  maximum  or  increasing  growth  about  1850,  1854-55,  1862-64,  1868-70,  1876, 
1882,  1886,  1894-96,  1902,  and  1908,  while  periods  of  minimum  growth  are  almost  as 
markedly  in  agreement.  If  a  time  unit  of  5  or  10  years  were  used  instead  of  one  year,  and 
if  the  proper  corrections  were  applied  to  eliminate  the  various  errors  due  to  age,  longevity, 
and  the  like,  the  five  curves  would  be  practically  identical.  This  supports  the  conclusions 
of  Professor  Douglass  as  to  the  possibility  of  obtaining  fairly  reliable  records  from  a  small 
number  of  trees.  Nevertheless,  there  can  be  little  doubt  that  much  more  accurate  results 
are  obtained  where  a  large  number  is  employed. 


1850  Date  1860  1870  1880  1890  1900  1910 


Fig.  44. — Growth  of  Trees  at  Hume,  and  Rainfall  at  Fresno. 

(See  Table  I,  pp.  328-329.) 

We  have  now  to  determine  how  far  the  synchronous  fluctuations  in  the  rate  of  growth 
of  these  five  groups  of  trees  are  due  to  variations  in  rainfall.  The  trees  of  all  the  groups  are 
scattered  over  an  area  of  about  a  mile  square.  No  fires  appear  to  have  occurred  in  the 
region  for  many  years,  certainly  not  during  the  last  30  or  40,  and  probably  not  for  centuries. 
The  trees  were  all  strong  and  vigorous  at  the  time  when  the  sections  were  cut,  and  there 
was  no  sign  that  they  were  influenced  by  any  special  diseases  or  parasites.  They  were 
scattered  in  all  sorts  of  locations,  from  places  where  swamps  or  perennial  brooks  bathed 
their  roots  to  dry,  rocky  hillsides  subject  to  constant  drought.  Unless  the  variations  in 
the  rate  of  growth  are  due  to  climate,  there  seems  to  be  no  adequate  explanation  of  their 
existence.  Nevertheless,  when  the  combined  curve  of  the  five  groups  is  placed  beside  the 
curve  of  rainfall  at  Fresno  and,  before  1882,  San  Francisco,  as  is  done  in  figure  44,  the 
degree  of  agreement  is  scarcely  so  great  as  one  would  expect.  The  combined  curve  of  the 
five  groups  is  obtained  by  using  all  of  the  111  trees  as  far  back  as  1884.  At  that  point  the 


164 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


37  trees  of  group  I  are  dropped  and  a  correction  is  applied,  as  explained  in  a  preceding 
chapter,  in  order  to  compensate  for  the  difference  between  the  average  rate  of  growth  of 
all  the  trees  and  that  of  the  74  trees  which  still  remain.  This  has  no  effect  whatever 
upon  the  form  of  the  sinuosities  of  the  curve;  it  merely  serves  to  prevent  it  from  dwindling 
away  in  its  earlier  portions,  and  to  prevent  the  dropping  of  trees  from  causing  apparent 
sinuosities  where  none  exist.  From  1883  back  to  1850  the  curve  is  based  on  74  trees. 
Then  group  II  is  dropped,  and  the  curve  is  based  on  25  trees  from  1849  to  1812.  Finally, 
14  of  the  trees  of  group  III  are  dropped,  leaving  only  9  which  carry  it  back  to  1766.  The 
earlier  portions  of  this  curve  do  not  appear  in  figure  44,  but  are  used  in  later  discussions. 

In  figure  44  a  certain  degree  of  agreement  can  be  seen  between  the  curve  of  growth 
and  the  curve  of  precipitation.  This  becomes  clearer  when  the  simple  rainfall  curve  is 
replaced  by  the  smoothed  curve  shown  in  the  middle  line.  This  smoothed  curve  is  made 
by  taking  the  mean  of  three  years’  rain  and  plotting  it  in  the  third  year  of  each  group 
of  three.  The  reason  for  plotting  it  in  the  third  year  instead  of  the  middle  year  is  that  the 
effect  of  a  rainy  season  can  not  possibly  be  felt  before  it  occurs,  but  is  felt  in  the  years 
succeeding  its  occurrence.  Between  the  smoothed  curve  of  precipitation  and  the  curve  of 
growth  a  considerable  degree  of  agreement  is  manifest.  For  instance,  the  rainfall  maxima 
of  1862, 1868, 1876, 1886, 1895-97, 1901,  and  1907  are  all  accompanied  or  closely  followed  by 
arboreal  maxima.  Marked  disagreement,  however,  is  evident  in  such  years  as  1878,  1882, 
and  1904.  The  explanation  of  these  discrepancies  seems  to  be  found  largely  in  the  seasonal 
distribution  of  the  precipitation,  as  is  shown  in  figure  45.  For  example,  the  smoothed 

rainfall  curve  rises  irregularly 
from  1871  to  1880,  and  judging 
from  the  10  years  before  this 
period  and  the  20  or  more  years 
following  it,  we  should  expect  the 
tree  curve  to  do  likewise.  Up  to 
1877  the  two  do  agree  very  well, 
but  then  comes  a  marked  discrep¬ 
ancy  lasting  till  1882.  Figure 
45  suggests  the  probable  cause 

of  this.  It  shows  the  average 

seasonal  distribution  of  precipitation  since  1850  at  San  Francisco  in  the  dotted  line,  while 
the  other  lines  show  the  distribution  for  special  years,  either  there  or  at  Fresno.  The  year 
1876-77  was  one  of  the  worst  on  record.  Not  only  was  the  rainfall  scanty,  but  its  distri¬ 
bution  was  perhaps  the  worst  since  records  have  been  kept.  October  was  rainy,  but  precipi¬ 
tation  in  that  month  is  of  little  use,  since  it  either  takes  the  form  of  rain,  or  else  having 
fallen  as  snow  it  melts  off  unless  promptly  covered  by  fresh  supplies.  No  new  snow  came 
in  either  November  or  December.  January  had  a  good  supply,  although  not  quite  the 
average  amount,  and  each  of  the  next  four  months  received  only  a  third  of  the  normal 

supply.  In  May  the  ground  must  have  been  as  dry  as  it  usually  is  in  August.  The 

growth  of  vegetation  must  have  been  checked  almost  as  soon  as  it  began,  and  the  trees 
must  have  suffered  sadly.  Apparently  they  were  so  injured  that  they  could  not  make  a 
good  growth  the  next  year  in  spite  of  abundant  precipitation,  well  distributed;  then  they 
began  to  recover,  and  by  1882  were  in  such  a  condition  that  they  grew  well  in  spite  of  scanty 
precipitation.  That  year,  however,  was  very  different  from  1877.  The  fall  and  early 
winter  were  dry,  but  February,  March,  and  April  equaled  or  exceeded  the  normal,  and 
those  are  apparently  the  most  important  months.  In  1904  a  similar  case  occurs:  The 
precipitation  remains  at  a  low  point,  but  the  growth  of  the  trees  is  accelerated.  The  cause 
seems  to  be  plainly  evident  in  the  unusually  large  fall  of  snow  or  rain  during  February, 
March,  and  April,  as  shown  in  figure  45.  Thus  we  might  go  on  to  analyze  year  after  year. 


Inches 


o  ^ 
c  • 

tfi  O'i 
O 


Fig.  45. — Mean  Monthly  Distribution  of  Rainfall  Compared  with  Distri¬ 
bution  in  Exceptional  Years.  San  Francisco-Fresno. 


INTERPRETATION  OP  THE  CURVE  OF  THE  SEQUOIA. 


165 


and  find  causes  for  a  large  number  of  the  divergencies  between  the  curves  of  growth  and 
precipitation. 

The  seasonal  distribution  of  rainfall,  however,  is  only  one  of  the  two  chief  factors  which 
cause  the  curve  of  the  trees  to  disagree  with  that  of  the  rain.  The  other  is  what  Professor 
Douglass  has  called  the  conversation  factor.  The  extent  to  which  the  curve  of  growth 
lags  behind  that  of  precipitation,  even  when  the  3-year  mean  rainfall  is  plotted  in  the  last 
of  the  3  years  of  any  given  group,  suggests  that  this  factor  plays  a  more  important  part 
here  than  among  the  pines  in  Arizona.  It  apparently  depends  not  only  upon  the  amount 
of  water  stored  in  the  soil,  but  upon  the  amount  of  reserve  strength  which  the  plant  has 
been  able  to  acquire  by  enlarging  its  root  system  or  by  the  growth  of  branches  and  buds. 

Figure  46  represents  the  result  of  the  most  satisfactory  of  five  or  six  methods  by  which 
an  attempt  has  been  made  to  gage  the  effect  of  the  rainfall  of  preceding  years  upon  the 
growth  of  the  sequoias  at  Hume  during  any  particular  year.  From  the  63  years  for  which 
records  of  rainfall  at  San  Francisco  and  Fresno  are  available  (that  is,  from  1849-50  to  1911- 
12)  I  have  selected  two  groups.  One  group  consists  of  15  years,  during  which  the  trees  at 
Hume  not  only  formed  rings  having  more  than  the  average  thickness  of  3.5  mm.  according 
to  the  corrected  figures  used  in  plotting  the  curve,  but  also  grew  faster  than  during  the 
preceding  year  by  an  amount  of  0.25  mm.  or  more.  The  other  group  consists  of  14  years, 
during  which  the  trees  not  only  grew  less  than  the  average  amount,  but  also  grew  less 
rapidly  than  during  the  preceding  years  by  an  amount  of  0.23  mm.  or  more.  This  last 
figure  was  selected  instead  of  0.25  mm.  simply  in  order  to  make  the  two  groups  as  nearly 
equal  as  possible.  In  the  selection  of  these  two  groups  it  is  clear  that  two  chief  criteria 
are  employed,  the  absolute  amount  of  growth  and  the  relative  amount.  A  glance  at  the 
curve  of  growth  in  figure  44,  the  upper  solid  line,  will  show  how  the  two  criteria  are  applied. 
According  to  the  first  criterion  (absolute  growth)  the  years  are  divided  into  two  classes. 
One  class  comprises  all  those  which  grew  more  than  3.5  mm.  and  whose  position  in  the 
diagram  is  above  the  median  horizontal  line,  while  the  other  class  comprises  all  which  grew 
less  than  3.5  mm.  and  whose  position  is  below  the  line.  From  the  class  of  rapidly  growing 
trees  a  smaller  class  was  selected  by  means  of  the  second  criterion,  relative  growth.  All  the 
3'ears  in  which  the  growth  was  more  than  0.25  mm.  in  excess  of  the  preceding  year,  or  in 
other  words  all  the  years  which  are  preceded  by  a  rapidly  rising  portion  of  the  curve  in 
figure  44,  were  selected  and  the  rest  rejected.  In  the  same  way,  among  the  slow-growing 
trees  selection  was  made  of  all  which  show  a  growth  of  0.23  mm.  or  more  in  deficiency  of 
the  preceding  year — that  is,  which  are  preceded  by  a  rapidly  falling  portion  of  the  curve. 

For  these  two  groups  of  years  of  rapid  and  increasing  growth  on  the  one  hand,  and  of 
slow,  decreasing  growth  on  the  other  hand,  I  have  calculated  the  average  rainfall,  first 
during  the  season  preceding  the  period  of  growth,  then  during  the  two  seasons  preceding  it, 
and  so  on  until  5  years  have  been  included.  The  results  appear  in  figure  46.  In  the 
figure  the  upper  curve  represents  the  rainfall  of  what  we  may  call  the  progressive  years, 
and  the  lower  of  the  reactionary,  while  the  solid  horizontal  line  indicates  the  mean  rainfall 
for  the  entire  period  of  62  years,  which  amounts  to  10.67  inches  for  Fresno.  The  meaning 
of  the  curves  is  plain.  During  the  years  immediately  preceding  times  of  rapid  and  increas¬ 
ing  growth  the  average  rainfall  was  12.58  inches;  for  the  period  of  2  years  preceding  such 
times  it  was  12.02  inches;  for  3  years  11.86  inches;  for  4  years  11.30  inches;  and  for  5  years 
11.17  inches,  a  series  of  figures  which  increases  steadily  as  the  times  of  rapid  growth  are 
approached.  In  the  case  of  the  slow-growing  trees,  on  the  contrary,  the  figures  are  for 
1  year  9.98  inches,  2  years  9.51,  3  years  9.64,  4  years  10.08,  and  5  years  10.53,  a  series  which, 
in  general,  decreases  as  the  times  of  slow  growth  are  approached.  If  the  two  curves 
were  carried  back  a  few  years  farther  they  would  coalesce.  Figure  47  illustrates  the  same 
thing  as  46,  except  that  the  mean  rainfall  for  the  first,  second,  third,  fourth,  and  fifth  years 
preceding  the  years  of  growth  has  been  plotted  instead  of  the  means  for  periods  of  1,  2,  3, 


166 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


4,  and  5  years.  In  either  case  it  is  obvious  that  the  most  favorable  growth  comes  at  the 
end  of  a  series  of  4  or  5  years  of  increasing  rainfall,  while  the  slowest  growth  follows  a  similar 
series  of  years  of  diminishing  rainfall.  In  the  case  of  slow  growth  we  see  evidence  that  a 
slight  improvement  in  the  amount  of  rainfall  is  not  able  to  overcome  the  harmful  effects 
of  a  preceding  series  of  bad  years.  Otherwise  the  curve  of  the  slow  years  would  not  hook 
up  at  the  right-hand  end,  showing  that  after  a  series  of  bad  years,  even  though  the  rainfall 
increases  somewhat,  the  trees  do  not  respond  at  once. 


Years  preceding  year  of  growth 


Years  preceding  year  of  growth 


Mean  rainfall  in  relation  to 
15  years  of  rapid  growth 


Mean  rainfall  for  62  years 
Mean  rainfall  in  relation  to 
14  years  of  slow  growth 


Fig.  46. — Conservation  Factor  in  the  Relation 
of  Growth  and  Rainfall,  Method  I. 


Fig.  47. — Conservation  Factor  in  the  Relation 
of  Growth  and  Rainfall,  Method  II. 


If  we  are  right  as  to  the  relation  of  the  rainfall  of  past  years  to  the  growth  of  the  sequoia 
during  any  particular  season,  it  ought  to  be  possible  to  reduce  this  relation  to  a  formula, 
just  as  in  the  case  of  the  yellow  pines  of  Arizona.  Professor  Douglass  has  kindly  consented 
to  work  out  the  formula.  It  is  given  below,  together  with  his  comments : 

“A  trial  of  the  ‘accumulated  moisture’  formula  of  the  yellow  pines  in  Arizona  shows  that 
it  does  not  apply  to  the  sequoias  of  California,  presumably  because  the  precipitation  is  heavier 
among  the  Sierras  than  in  the  plateaus  of  Arizona.  An  ‘additive’  formula,  on  the  other  hand, 
gives  an  encouraging  result,  as  is  shown  in  the  accompanying  diagram  (figure  48).  This  formula 
allows  for  strong  conservation  by  the  soil,  not  of  the  static  type,  as  in  a  pond,  but  of  the  moving 
type  as  if  a  belated  supply  from  the  snows  came  to  hand  and  then  passed  on.  The  tree,  then, 
has  moisture  from  the  current  year  and  from  the  first  and  second  preceding  years;  and  whichever 
of  the  three  is  greater,  that  one  has  the  more  effect.  The  formula  is 

rp  _  rr  ~l~  fin-1  +  Kn-2 

Rn  +  Rn-l  +  Rn-i 

This  is  of  course  empirical  and  will  be  improved.  It  is  worthy  of  study  as  illustrating  what 
appears  to  be  a  difference  in  type  of  formula  for  different  climates.  Without  doubt  the  reversal 
of  this  formula  to  ascertain  rainfall  from  tree  growth  is  much  more  difficult  than  that  of  the  Arizona 
formula,  for  the  tree  automatically  smooths  the  rainfall  variations,  but  variations  of  a  longer  period 
than  three  years  will  be  evident.” 

The  gist  of  the  relation  of  the  growth  of  the  sequoias  to  precipitation  may  be  stated  in 
a  few  words.  In  the  regions  whence  our  measurements  have  been  obtained  the  growth 
depends  primarily  upon  the  amount  of  rainfall,  but  almost  equally  upon  its  monthly  dis¬ 
tribution.  Owing  to  the  conservation  factor  the  rainfall  of  any  single  year  is  only  one  of 
the  factors  which  determine  the  amount  of  growth.  Only  by  taking  a  period  of  3  or  more 
years  can  we  form  an  accurate  judgment  as  to  the  actual  amount  of  growth  which  corre¬ 
sponds  to  a  given  rainfall.  Where  a  longer  period  than  5  years  is  concerned  we  may  say 
with  confidence  that,  if  due  allowance  is  made  for  age,  longevity,  and  other  factors,  the 
thickness  of  the  rings  of  growth  is  dependent  upon  the  amount  and  season  of  the  rainfall. 
Excessive  precipitation  may,  perhaps,  in  some  cases  check  growth,  but  as  yet  no  evidence 


INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


167 


of  this  has  been  noticed,  even  in  years  where  the  precipitation  amounts  to  two  or  three 
times  the  average.  In  the  past,  it  seems  safe  to  say,  the  relation  of  precipitation  and  growth 
must  have  been  essentially  the  same  as  at  present.  Therefore  we  seem  warranted  in 
concluding  that  in  our  long  curve  of  growth,  extending  back  3,000  years,  and  given  in 
figures  38  and  50,  high  places  indicate  abundant  moisture  and  low  places  indicate  drought. 
How  greatly  the  rainfall  of  the  past  exceeded  that  of  the  present  we  can  not  yet  ascertain 


Fig.  48. — Tree  Growth  in  California  Calculated  from  Rainfall,  by  A.  E.  Douglass. 

(See  Table  I,  pp.  328-329.) 

positively.  In  the  modern  sequoias  the  growth  during  the  group  of  15  favorable  years 
exceeded  that  during  the  14  unfavorable  years  by  0.43  mm.,  or  12.3  per  cent  of  the  mean. 
The  rainfall  during  the  periods  of  5  years  preceding  the  favorable  years  exceeded  that 
during  the  similar  periods  preceding  the  unfavorable  years  by  0.64  inch,  or  6  per  cent 
of  the  mean,  while  if  a  4-year  period  is  taken  instead  of  5  the  excess  is  1.22  inches,  or  14.3 
per  cent.  From  this  it  would  appear  that  the  thickness  of  the  rings  of  growth  is  closely 
proportional  to  the  rainfall.  By  this  I  do  not  mean  to  be  understood  as  making  any 
exact  or  positive  statement,  but  merely  as  indicating  the  order  of  magnitude  of  the  relative 
changes  of  rainfall  and  growth.  Increasing  the  rainfall  by  10  per  cent  might  increase  the 
thickness  of  the  rings  by  5  per  cent  or  20  per  cent,  but  it  is  quite  certain  that  it  would 
not  increase  the  thickness  by  50  per  cent,  nor  would  its  effect  be  so  small  as  1  per  cent. 

Before  attempting  an  analysis  of  the  changes  of  climate  indicated  by  the  long  curve 
of  the  sequoia,  let  us  attempt  to  gain  some  light  on  the  nature  of  the  monthly  distribution 
of  the  rainfall  and  the  seasonal  variations  in  storminess  during  favorable  as  compared 
with  unfavorable  years.  Because  of  the  projection  of  the  effects  of  past  years  into  those 
that  follow,  that  is,  because  of  the  conservation  factor,  it  is  not  easy  to  ascertain  exactly 
how  much  influence  is  to  be  attributed  to  the  seasonal  distribution  of  the  rain  of  a  single 
year.  Yet  we  have  seen  that  this  is  a  highly  important  factor.  If  the  precipitation  all  came 
in  the  form  of  rain  in  the  fall,  or  if  it  all  fell  as  snow  after  the  ground  was  frozen  and  then 
was  rapidly  melted  by  heavy  rains  in  the  early  spring,  the  effect  upon  trees  would  be  quite 
different  from  that  which  would  result  from  a  uniform  distribution  throughout  the  fall, 
winter,  and  spring,  or  from  heavy  precipitation  from  February  to  May. 

Four  ways  of  testing  the  matter  suggest  themselves:  (A)  First  we  may  pay  attention 
only  to  the  amount  of  moisture  and  may  compare  years  of  exceptionally  heavy  and 
exceptionally  Ught  precipitation.  (B)  Next  we  may  pay  attention  only  to  the  growth 


168 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  the  trees  and  may  compare  the  years  of  rapid  growth  with  those  of  slow  growth,  using 
the  two  groups  that  we  have  already  employed  in  our  study  of  the  conservation  factor. 
(C)  Again  we  may  combine  growth  and  rainfall,  and  compare  two  groups  of  years,  in  one 
of  which  both  the  rate  of  growth  and  the  rainfall  increase  in  amount,  and  in  the  other  of 
which  both  quantities  decrease.  (D)  And  finally  we  may  combine  growth  and  rainfall  in 
still  another  way,  forming  two  groups  of  years  in  one  of  which  both  the  rainfall  and  the 
rate  of  growth  are  above  the  normal  and  in  the  other  of'which  both  are  below  the  normal. 


Table  7. — Groups  of  favorable  and  unfavorable  years  in  California. 


Years. 

A 

B 

c 

D 

E 

Favor¬ 

able. 

Unfav¬ 

orable. 

Favor¬ 

able. 

Unfav¬ 

orable. 

Favor-' Unfav- 
able.  1  orable. 

Favor¬ 

able. 

Unfav¬ 

orable. 

Favor¬ 

able. 

Unfav¬ 

orable. 

1849-50 _ 

X 

X 

X 

1850-1 . 

0 

0 

0 

1851-2 . 

1852-3 . 

X 

X 

X 

X 

1853-4 . 

. 

1854-5 . 

1855-6 . 

0 

0 

0 

1856-7 . 

0 

0 

0 

1857-8 . 

X 

0 

1858-9 . 

0 

0 

0 

1859-60 _ 

0 

1860-1 . 

0 

1861-2 . 

X 

X 

X 

X 

X 

1862-3 . 

0 

0 

0 

0 

1863-4 . 

0 

1864-5 . 

0 

186.5-6 . 

1866-7 . 

X 

1867-8 . 

X 

X 

X 

X 

X 

1868-9 . 

X 

1869-70 _ 

1870-1 . 

0 

0 

0 

0 

0 

1871-2 . 

X 

0 

1872-3 . 

0 

0 

0 

1873-4  . 

X 

X 

X 

1874-5 . 

0 

0 

1875-6 . 

X 

X 

X 

X 

X 

1876-7 . 

0 

0 

0 

0 

0 

1877-8 . 

X 

1878-9 . 

1879-80 _ 

X 

X 

X 

1880-1 . 

X 

0 

1881-2 . 

0 

X 

1882-3 . 

X 

0 

0 

0 

1883-4 . 

X 

X 

X 

1884-5 . 

0 

X 

X 

1885-6 . 

X 

X 

X 

X 

X 

1886-7 . 

0 

1887-8 . 

0 

0 

0 

0 

0 

1888-9 . 

0 

X 

1889-90 _ 

X 

0 

1890-1 . 

X 

1891-2 . 

0 

1892-3 . 

0 

1893-4 . 

X 

1894-5 . 

X 

X 

X 

X 

X 

1895-6 . 

1896-7 . 

1897-8 . 

0 

0 

0 

1898-9 . 

0 

0 

0 

0 

1899-1900. . 

1900-1 . 

X 

0 

1901-2 . 

0 

0 

0 

1902-3 . 

. 

0 

1903-4 . 

X 

1904-5 . 

X 

0 

1905-6 . 

X 

0 

1906-7 . 

0 

1907-8 . 

X 

1908-9 . 

Total  years. . 

16 

14 

14 

12 

11 

12 

9 

17^ 

~lo 

~13 

INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


169 


In  each  of  these  four  cases  we  have  a  group  of  favorable  years  to  be  compared  with  a  group 
of  unfavorable.  The  comparison  can  most  easily  be  made  by  means  of  a  series  of  diagrams 
showing  the  average  amount  of  rain  for  each  month  in  each  group  of  years.  This  is  done 
in  figure  49,  where  the  solid  lines  represent  the  favorable  years,  the  dash  lines  the  un¬ 
favorable,  and  the  intermediate  dotted  lines  the  mean  for  all  years.  The  dates  and  figures 
on  which  the  curves  are  based  are  given  in  tables  7  and  8.  From  table  7  it  appears  that 
29  years  are  included  in  one  or  another  of  the  favorable  groups;  18  of  these  are  included  in 
only  one  favorable  group,  3  are  in  two  groups,  2  are  in  three  groups,  and  6  are  in  four. 
The  unfavorable  groups  include  35  years,  20  of  which  are  included  in  only  one  group,  9 
in  two,  2  in  three,  and  4  in  four.  Only  10  years  fail  to  fall  in  any  group,  while  12  fall  in 
both  a  favorable  and  an  unfavorable  group.  One  of  these  last,  1874-75,  falls  in  one 
favorable  group  and  two  unfavorable.  Omitting  all  years  which  fall  in  only  one  group, 
or  in  both  favorable  and  unfavorable  groups,  there  remain  11  which  fall  in  two  or  more 
favorable  groups  and  14  which  fall  in  two  or  more  unfavorable  groups.  These  25  years 
form  two  final  groups  (E  in  the  tables)  representing  the  extremes  of  the  two  conditions 
with  which  we  have  to  deal.  The  average  monthly  distribution  of  rainfall  in  them  has 
been  plotted  as  the  last  of  the  sets  of  curves  in  figure  49,  and  may  be  regarded  as  the  most 
typical. 


Table  8. — Mean  monthly  rainfall  {in  inches)  of  the  groups  of  favorable  and  unfavorable  years  shown  in  table  7. 


July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

1  Favorable . 

0.00 

0.00 

0.17 

0,67 

1.98 

3.48 

3.43 

2.28 

1.89 

1.33 

0.52 

0.11 

(  Unfavorable. . . . 

0.00 

0.00 

0.22 

0.41 

0.55 

1.13 

1.02 

0.94 

1.14 

0.61 

0.27 

0.05 

f  Favorable . 

0.00 

0.00 

0.18 

0.30 

1.39 

2.42 

2.95 

2.02 

1.69 

1.15 

0.35 

0.19 

(  Unfavorable.. . . 

0.00 

0.02 

0.35 

0.99 

1.02 

1.92 

1.79 

1.14 

1.58 

0.43 

0.72 

0.10 

f  Favorable . 

0.00 

0.00 

0.09 

0.39 

2.45 

2.55 

3.35 

1.73 

1.87 

1.54 

0.37 

0.16 

c. 

(  Unfavorable.... 

0.00 

0.00 

0.07 

0.46 

0.62 

1.56 

1.88 

1.45 

1.04 

0.08 

0.22 

0.08 

(  Favorable . 

0.00 

0.00 

0.09 

0.46 

2.67 

3.56 

4.16 

2.00 

2.17 

1.39 

0.33 

0.10 

1  Unfavorable .... 

0.01 

0.01 

0.20 

0.40 

1.08 

1.50 

1.49 

1.36 

1.49 

0.59 

0.45 

0.05 

(  Favorable . 

0.00 

0.01 

0.08 

0.45 

2.59 

3.39 

3.85 

1.87 

2.05 

1,71 

0.35 

0.15 

hi. 

I  Unfavorable.... 

0.00 

0.01 

0.25 

0.53 

0.57 

1.33 

1.46 

1.77 

1.35 

0.52 

0.40 

0.00 

A  comparison  of  the  curves  of  figure  49  is  interesting.  In  group  A,  16  years  with  12 
inches  of  rain  are  compared  with  14  having  less  than  8  inches.  Both  curves  are  here  quite 
regular,  and  in  general  form  resemble  the  mean  curve  for  the  entire  60  years  since  records 
have  been  kept.  In  all  three  precipitation  increases  from  July  to  December,  and  decreases 
from  January  to  June,  the  only  marked  exception  being  February  in  the  curve  for  years 
of  low  rainfall.  The  work  of  Professor  Kulhner,  as  explained  later,  shows  that  during 
the  favorable  years  of  this  group  the  storminess  of  the  United  States  as  a  whole  slightly 
exceeded  the  average,  while  during  the  unfavorable  years  it  was  distinctly  less.  The 
next  set  of  curves  indicates  the  distribution  of  precipitation  during  14  years  of  uncom¬ 
monly  favorable  growth  and  12  years  of  uncommonly  unfavorable  growth,  no  attention 
being  paid  to  the  amount  of  rainfall.  The  position  of  the  curve  for  the  favorable  years 
above  that  for  unfavorable  years  from  November  to  April,  inclusive,  indicates  that 
the  growth  of  the  trees  is  strongly  influenced  by  the  amount  of  rain  during  the  preceding 
winter.  But  the  fact  that  these  two  curves  are  much  closer  to  one  another  than  are  the 
two  representing  groups  of  years  selected  solely  upon  the  basis  of  rainfall  emphasizes  the 
conclusion  already  reached  that  the  amount  of  growth  depends  upon  the  rainfall  of  a  con¬ 
siderable  number  of  past  years,  not  upon  that  of  one  year  alone.  The  next  two  sets  of 
curves  represent  12  favorable  and  12  unfavorable  years  selected  because  of  the  criteria 
mentioned  under  C,  and  9  favorable  and  17  unfavorable  years  of  the  type  D.  Inasmuch 
as  both  of  these  sets  are  based  on  the  relation  of  rainfall  and  growth  rather  than  upon  either 


170 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


one  alone,  they  give  a  truer  impression  than  do  the  preceding  sets.  Finally,  the  curves  of 
the  last  set,  E,  representing  10  favorable  and  13  unfavorable  years,  which  combine  special 
conditions  of  both  rainfall  and  growth  in  the  highest  degree,  deserve  careful  consideration. 
They  present  the  same  general  appearance  as  the  other  two  sets  of  curves  which  combine 
our  two  factors,  but  in  a  higher  or  more  intensified  degree.  During  the  four  months 
from  July  to  October,  inclusive,  all  three  curves,  favorable,  mean,  and  unfavorable,  practi¬ 
cally  coincide;  then  in  November  the  favorable  curve  jumps  to  a  great  height,  indicating 
an  abundant  fall  of  snow  at  the  beginning  of  winter,  while  the  unfavorable  curve  remains 

horizontal,  indicating  an  open  season  with 
4  only  a  few  inches  of  snow.  Throughout 

3  December  and  January  the  favorable  curve 

2  remains  far  above  the  unfavorable,  in  Feb¬ 
ruary  the  two  almost  coalesce,  while  in 

^  March  and  April  the  favorable  curve  is 

0  somewhat  higher  than  the  other,  although 

4  by  no  means  so  much  so  as  during  the  first 

3  part  of  the  winter.  Early  snows  aid  the 

growth  of  trees  by  keeping  the  ground  almost 

^  unfrozen  and  thus  allowing  the  melting  snow 

1  to  sink  in  and  thoroughly  saturate  the  soil. 

0  In  addition  to  this  the  absence  of  frost  in 

4  5-  the  ground  permits  the  trees  to  begin  grow- 
l"  ing  almost  as  soon  as  the  snow  disappears, 

^  2.  and  thus  the  growing  season  is  lengthened,  a 

2  matter  which  is  of  especial  importance  in  a 

1  -a  region  like  the  Sierras,  where  the  drought  is 
Q  g  extreme.  The  effect  of  late  snows,  or  spring 

I  rains,  on  the  other  hand,  is  more  direct  and 
hence  still  more  important. 

^  The  climatic  conditions  indicated  by 

2  the  curves  of  figure  49  can  be  interpreted  in 

1  terms  of  cyclonic  storms.  Part  of  the  precipi- 

^  tation  of  the  Sierras  is  derived  from  cyclonic 

storms.  The  growth  of  the  trees  appears 
^  to  be  especially  promoted  in  years  when  the 

3  storms  begin  early  and  continue  late.  Al- 

2  though  the  sub j  ect  has  not  yet  been  well  inves- 

j  tigated,  it  appears  that  during  such  winters 

the  storms  move  farther  south  than  usual. 
^  Possibly  an  indirect  indication  of  this  is  found 
in  the  rapid  decrease  of  precipitation  during 
February.  In  winters  of  the  type  character¬ 
istic  of  northern  regions  the  storms  begin 
early  in  the  season  and  there  is  a  rapid  in¬ 
crease  in  the  amount  of  precipitation;  then,  as 
winter  conditions  come  to  prevail  completely  and  the  continent  becomes  thoroughly  chilled, 
a  great  continental  area  of  high  pressure  and  low  temperature  is  developed.  This  prevents 
storms  in  the  area  where  it  prevails  and  gives  rise  to  calm,  clear  weather,  bitter  cold  perhaps, 
but  sunny  and  free  from  wind.  The  storms  meanwhile  are  pushed  to  the  edges  of  the 
area  of  high  pressure — that  is,  toward  the  oceans  and  the  south.  Then,  when  spring 
approaches  and  the  high-pressure  area  is  broken  up,  storms  once  more  prevail,  but  not  with 


Jul.Aug.  Sep.  Oct.  Nov.Dec.  .Ian.  Feb.Mar.Apr.May  Jun. 


Fig.  49. — Rainfall  by  Months  in  Favorable 
and  Unfavorable  Years. 

Mean  of  all  Years  =  . 

Unfavorable  Years  - - 

Favorable  Years  =  - 


INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


171 


such  severity  as  during  the  first  part  of  the  winter,  for  they  are  soon  affected  by  the  coming 
on  of  the  conditions  which  prevail  in  summer  when  the  winds  are  weaker  than  in  winter. 
When  winters  of  this  type  prevail  in  California,  the  ordinary  California  type  is  pushed 
farther  south.  At  such  times  regions  like  southern  Arizona  would  probably  get  as  many 
storms  as  Utah  now  gets,  while  places  as  remote  as  the  Gulf  of  Mexico  would  be  visited 
by  frequent  “northers.” 

Meanwhile  our  general  conclusion  may  be  summed  up  thus:  Judging  from  what  we 
have  seen  of  the  rainfall  of  to-day  and  of  its  relation  to  the  growth  of  the  sequoias,  high 
portions  of  their  curve  seem  to  indicate  periods  when  the  winters  were  longer  than  now,  when 
storms  began  earlier  in  the  fall  and  lasted  later  into  the  spring,  and  when  mid-winter  was 
characterized  by  the  great  development  of  a  cold,  continental,  high-pressure  area,  which 
pushed  the  storms  of  the  zone  of  prevailing  westerly  winds  far  down  into  subtropical  regions 
and  thus  caused  subtropical  conditions  to  invade  what  is  now  the  zone  of  equatorial  rains. 

With  this  interpretation  of  the  curve  of  the  sequoias  before  us,  we  are  prepared  to 
consider  its  meaning  in  reference  to  the  history  of  the  world  as  a  whole.  Figure  50  shows  a 
dotted  line  representing  the  approximate  climatic  fluctuations  of  historic  times  as  given 
diagrammatically  on  pages  327  and  403  of  “Palestine  and  its  Transformation.”  Leaving 
out  of  account  the  slope  of  the  sequoia  curve  to  correspond  with  the  changes  in  level  of 
the  Caspian  Sea,  let  us  see  to  what  extent  these  two  entirely  independent  curves  of  tree 
growth  in  California  and  of  climatic  pulsations  in  Asia  agree.  The  number  of  maxima 
in  the  Asiatic  curve  is  far  less  than  in  the  one  from  California,  but  this  is  of  no  special 
significance.  By  its  very  nature  the  Asiatic  curve  is  a  mere  approximation  and  can  not 
be  expected  to  show  minute  details.  The  evidence  on  which  it  is  based,  especially  in 
the  early  portions,  is  so  scanty  that  long  gaps,  sometimes  100  or  200  years  in  length, 
may  intervene  between  two  points  for  which  data  are  available.  In  such  cases  the  method 
adopted  was  to  draw  a  straight  line  between  the  points  regardless  of  the  fact  that  fluctu¬ 
ations  of  much  importance  may  have  taken  place  in  the  interval.  Moreover,  even  though 
the  Asiatic  lines  of  evidence  point  to  exceptional  aridity  or  moisture,  we  can  not  in  most 
cases  be  sure  that  they  indicate  the  dates  when  those  conditions  reached  a  maximum. 
For  example,  we  find  evidence  of  aridity  both  before  and  after  1200  a.  d.,  while  moist  con¬ 
ditions  are  indicated  in  1000  a.  d.  and  1325  a.  d.,  but  we  can  not  be  sure  that  these  are 
exactly  the  times  of  the  true  maxima  and  minima  of  rainfall,  nor  can  we  be  certain  as  to 
whether  the  dry  periods  or  the  moist  periods  were  more  prolonged.  Hence  it  is  a  pure 
matter  of  personal  judgment  whether  we  shall  draw  a  U-shaped  or  a  V-shaped  curve. 
In  addition  to  all  this  it  has  thus  far  been  generally  impossible  to  determine  how  low  a 
given  depression  should  fall.  For  example,  at  300  a.  d.,  650  a.  d.,  and  1200  a.  d.  evidences 
of  increasing  aridity  are  especially  noticeable;  hence  the  curve  drops  deeply.  Yet  so  far 
as  the  actual  facts  are  concerned  the  lines  might  have  been  drawn  as  indicated  by  the 
dashes.  Finally,  although  the  writer  was  not  at  the  time  conscious  of  it,  the  exact  form 
of  the  Asiatic  curve  was  determined  in  some  respects  by  a  preconceived  idea  which  now 
appears  to  be  erroneous.  The  idea  was  that  changes  of  climate  must  be  gradual  and  that 
lines  with  sharp  angles  and  sudden  risings  or  fallings  could  not  possibly  represent  the  facts. 
This,  for  example,  prevented  the  maximum  in  the  sixth  century  from  being  placed  as  late 
as  certain  ruins  would  suggest.  Inasmuch  as  everything  pointed  to  extreme  aridity 
about  625  a.  d.,  it  was  supposed  that  the  change  toward  that  aridity  must  have  begun  at 
least  half  a  century  or  more  prior  to  that  time;  it  was  not  realized  that  a  moderate  change 
might  occur  suddenly  when  conditions  were  already  none  too  favorable,  and  might  produce 
the  same  results  as  a  greater  change  acting  less  rapidly.  Taking  the  Asiatic  curve  as  a 
whole,  then,  we  must  bear  in  mind  that  it  is  only  a  preliminary  sketch,  a  pioneer  attempt 
to  elucidate  a  most  complex  subject,  and  that  the  necessity  for  visualizing  our  conclusions 
in  the  form  of  a  curve  compelled  the  making  of  a  large  number  of  more  or  less  important 
assumptions. 


172 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA, 


Bearing  in  mind,  then,  the  limitations  of  the  Asiatic  curve,  let  us  compare  it  with  the 
main  features  of  its  fellow  from  California.  At  the  beginning  the  two  curves  take  a  sudden 
drop  in  close  harmony,  a  rather  remarkable  coincidence,  but  one  that  must  not  be  much 
emphasized,  since  the  California  curve  is  based  on  a  single  tree  and  the  Asiatic  curve  on 
the  evidence  of  a  few  famines  and  an  uncommon  degree  of  movement  among  the  peoples 
of  the  lands  around  the  eastern  Mediterranean.  Next  we  get  pronounced  disagreement, 


but  this  is  less  significant  than  the  pervious  agreement.  It  may  be  due  simply  to  absence 
of  data  in  compiling  the  Asiatic  curve.  Between  1200  and  950  b.  c.  no  climatic  data 
whatever  had  come  to  light  in  Asia  when  the  curve  was  drawn;  hence  these  two  points  were 
connected  by  a  straight  line.  If  our  information  had  been  fuller  we  might  have  been  led 
to  draw  a  curve  similar  to  that  of  the  sequoias,  although  less  exaggerated.  At  950  b.  c. 
both  curves  show  a  decided  maximum.  Then  for  250  or  275  years  they  swing  downward 
and  again  upward,  smoothly  in  one  case  and  with  many  minor  variations  in  the  other,  and 
reach  maxima  at  690  and  660  b.  c.,  respectively.  Considering  the  fact  that  the  tree  curve 
is  much  exaggerated  because  this  portion  is  founded  on  so  few  trees,  while  the  other  curve 
is  based  on  very  scanty  historical  data,  the  agreement  may  be  considered  close.  Next, 
both  curves  drop  to  a  minimum  in  600  b.  c.,  after  which  the  trees  rise  to  a  marked  maximum 
in  400  B.  c.,  while  the  Asiatic  curve  rises  only  a  httle  and  has  no  corresponding  maximum. 
Here,  once  more,  we  have  a  distinct  disagreement.  It  is  more  significant  than  that  of  the 
twelfth  century  b.  c,  because  it  comes  later  when  the  number  of  trees  is  larger  and  historical 
records  more  numerous  than  six  centuries  before,  but  it  is  of  the  same  general  type.  In  the 
period  from  600  b.  c.  to  300  b,  c.  the  Asiatic  curve  is  drawn  as  a  straight  line  because  of  the 
absence  of  any  positive  data  during  that  long  interval.  If  further  information  were  at 
hand  the  Asiatic  curve  would  undoubtedly  be  sinuous,  and  the  few  scraps  of  evidence 
available  indicate  that  it  quite  certainly  would  not  be  low  at  400  b.  c.  and  probably  would 
be  high.  The  next  maximum  comes  at  300  b.  c.  in  one  curve  and  280  in  the  other,  a  good 
agreement.  The  succeeding  minima  culminate  nearly  100  years  apart,  but  here  again 
the  basis  of  the  Asiatic  cimve  is  merely  evidence  of  heavy  precipitation  about  300  b.  c. 
and  of  low  precipitation  150  years  later.  There  is  nothing  to  show  how  far  the  curve 
should  depart  from  a  straight  line  or  the  exact  point  where  it  should  be  at  a  minimum. 
Here,  then,  as  in  the  twelfth  century  b.  c.  and  at  400  b.  c.  the  two  curves  disagree,  but 
the  disagreement  is  of  a  purely  negative  character  and  hence  of  no  great  significance. 
For  the  next  380  years,  from  about  130  b.  c.  to  250  a.  d,,  the  curves  agree  to  a  remarkable 
extent.  Then  comes  a  disagreement,  the  first  which  is  genuinely  positive  and  hence 
significant.  The  pronounced  Asiatic  minimum  at  300  a.  d.  indicates  one  of  two  things. 
Either  the  climate  of  Asia  at  that  time  suffered  a  change  which  did  not  affect  California, 
or  else  a  distinct  mistake  has  been  made  in  the  Asiatic  curve.  In  view  of  the  close  agree¬ 
ment  of  other  portions  of  the  curve  I  am  inclined  to  the  second  supposition.  The  fact  that 
indications  of  aridity  happened  to  be  especially  well  preserved  at  the  time  has  probably 


INTERPRETATION  OF  THE  CURVE  OF  THE  SEQUOIA. 


173 


caused  me  to  carry  the  Asiatic  curve  lower  than  is  justifiable.  It  is  possible  that  there 
really  was  a  disagreement  between  Asia  and  America,  but  it  is  more  probable  that  the 
concentration  of  evidences  of  aridity  in  the  way  of  abandoned  ruins  and  the  like  at  that 
particular  period  led  me  to  infer  a  pronounced  minimum  at  a  date  when  there  was  merely 
a  greater  degree  of  aridity  than  hitherto,  although  not  so  great  a  degree  as  ensued  within  a 
century  or  tw'o.  In  general,  as  has  already  been  said,  the  three  noticeable  depressions 
in  the  Asiatic  curve,  namely,  those  in  300,  650,  and  1200  a.  d.,  are  probably  exaggerated, 
because  special  events,  due  apparently  to  increasing  aridity,  happened  to  culminate  at 
about  those  dates.  Yet  each  of  the  three  comes  at  a  time  of  increasing  aridity  in  the 
sequoia  curve,  and  in  the  case  of  the  minima  of  650  and  1200  a.  d.  the  sequoia  curve  is  also 
close  to  its  lowest  point. 

Returning  now  to  our  minute  survey  of  the  curves,  the  maximum  at  400  a.  d.  in  the 
Asiatic  curve  is  wholly  out  of  harmony  with  the  California  curve  as  it  now  stands.  If, 
however,  the  minimum  of  300  a.  d.  is  a  mistake,  the  succeeding  maximum  becomes  merely 
a  place  where  the  descent  of  the  curve  is  checked,  just  as  in  the  tree  curve.  From  400  to 
550  A.  D.  the  curves  agree.  The  maxima  of  550  in  Asia  and  610  in  California  are  probably 
identical,  although  for  reasons  already  explained  the  Asiatic  curve  drops  too  soon.  In  the 
next  section,  from  600  a.  d.  to  1500  a.  d.,  if  allowance  is  made  for  the  exaggeration  of  the 
Asiatic  minima,  the  two  curves  agree  closely  for  900  years.  Here,  as  at  the  time  of  Christ, 
the  agreement  is  such  that  it  can  scarcely  be  a  matter  of  chance.  After  1500  the  small 
fluctuations  agree  to  about  the  same  degree  as  do  the  large  ones  for  the  preceding  2,000 
years.  The  general  trend  of  the  American  curve  is  upward,  however,  and  that  of  the 
Asiatic  slightly  downward.  In  this  case  the  Asiatic  curve  is  probably  correct,  for  it  is 
based  largely  on  recorded  levels  of  the  Caspian  Sea.  The  American  curve,  on  the  other 
hand,  is  probably  wrong.  This  is  the  portion  which  is  most  seriously  subject  to  errors  due 
to  the  flaring  of  the  sequoias  at  the  base  of  the  trunk.  A  slight  correction  has  been  applied 
for  this,  as  already  stated,  but  from  the  scarcity  of  young  trees  and  from  the  general 
agreement  of  California  with  other  regions,  it  seems  as  if  this  correction  should  have  been 
greater.  Probably  the  curve  during  the  nineteenth  century  should  be  in  the  position 
indicated  by  the  fine  dotted  line  in  figures  50  and  54. 

The  conclusions  to  be  drawn  from  our  two  independent  methods  of  investigating  the 
climate  of  the  past  may  now  be  summed  up.  Three  points  stand  out  with  especial  clear¬ 
ness.  First  and  clearest,  important  climatic  pulsations  have  apparently  been  in  progress 
throughout  the  historical  period.  They  have  a  length  of  centuries,  but  do  not  show 
any  regular  periodicity.  They  are  often  characterized  by  sudden  changes  of  considerable 
magnitude.  The  agreement  of  all  our  lines  of  evidence  appears  to  establish  the  reality  of 
the  pulsations  upon  so  firm  a  basis  that  there  seems  little  likelihood  that  future  work  will 
put  it  in  question.  Doubtless  the  details  of  our  curves  will  be  altered,  but  their  sinuous 
character  with  its  indications  of  climatic  pulsations  is  not  likely  to  be  destroyed. 

In  the  second  place,  climatic  pulsations  in  western  America  and  in  similar  latitudes  in 
western  and  central  Asia  are  probably  synchronous  and  of  the  same  type.  This  conclusion 
is  by  no  means  so  firmly  established  as  is  the  reality  of  the  pulsations,  but  it  possesses  a 
high  degree  of  probability.  In  the  3,200  years  covered  by  our  two  curves  only  the  200 
years  from  250  to  400  a.  d.  and  550  to  600  a.  d.  show  positive  disagreements  which,  if 
confirmed,  would  militate  against  the  conclusion  just  reached.  During  a  much  longer 
period,  about  800  years  all  told,  the  two  curves  show  negative  disagreements,  not  due  like 
the  others  to  the  direct  interpretation  or  misinterpretation  of  actual  facts,  but  to  the 
mere  absence  of  data.  Finally,  for  2,200  years  the  two  curves  are  in  essential  harmony  so 
far  as  their  main  fluctuations  are  concerned.  Considering,  then,  the  imperfections  of  the 
Asiatic  curve  and  the  fact  that  the  respects  wherein  it  disagrees  with  the  American  curve 
are  those  where  it  is  known  to  be  most  liable  to  error,  we  may  regard  it  as  highly  probable 


174 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


that  the  main  climatic  pulsations  of  the  temperate  portions  of  central  and  western  Asia 
agree  with  those  of  the  same  latitude  in  western  America.  If  these  two  regions,  10,000 
miles  apart,  thus  agree,  it  seems  probable  that  in  regions  lying  in  the  same  latitude  and 
having  the  same  seasonal  distribution  of  rainfall,  similar  changes  must  have  taken  place 
all  around  the  globe,  or  at  least  over  all  the  continents,  while  corresponding,  although  not 
necessarily  similar,  changes  must  have  occurred  in  other  latitudes.  An  apparent  corollary 
of  this  conclusion  is  that  these  changes  were  due  to  a  shifting  of  the  world’s  climatic  zones 
because  of  an  alternate  increase  and  decrease  in  the  intensity  of  atmospheric  movements, 
but  this  corollary  has  by  no  means  the  same  degree  of  probability  as  the  main  conclusion 
whose  verity  it  in  no  wise  affects. 

The  third  of  our  conclusions  depends  upon  the  verity  of  the  first  two.  The  agreement 
of  the  mathematically  derived  curve  of  the  sequoias  with  the  Asiatic  curve  based  on  totally 
different  kinds  of  evidence  seems  to  confirm  the  validity  of  the  methods  employed  in  dealing 
with  those  other  kinds  of  evidence.  This  confirmation  has  important  consequences. 
In  all  studies  of  the  climate  of  the  past  it  is  far  easier  to  see  and  interpret  signs  of  the 
general  prevalence  of  relatively  moist  conditions  than  to  see  and  interpret  the  signs  of 
climatic  pulsations.  On  this  rock,  almost  without  exception,  careful  students  of  the 
subject  have  come  to  grief,  for  as  soon  as  they  have  perceived  evidences  of  a  degree  of 
aridity  in  remote  historic  times  at  all  approaching  that  of  to-day,  they  have  jumped  to  the 
conclusion  that  such  conditions  have  prevailed  alwaj'^s,  instead  of  only  temporarily.  If 
the  methods  which  were  first  employed  in  Asia  and  Greece,  and  have  now  been  applied 
to  America,  as  set  forth  in  the  first  part  of  this  volume,  are  competent  to  accompfish  the 
task  of  correctly  dating  the  chief  climatic  pulsations,  it  seems  as  if  they  must  be  competent 
to  accomplish  the  easier  task  of  determining  whether  the  climate  of  the  past  as  a  whole 
was  different  from  that  of  the  present.  They  point  to  this  conclusion  more  strongly  than 
to  that  of  pulsatory  changes.  Hence  we  conclude  not  only  that  the  climate  of  both  America 
and  Asia  has  been  subject  to  pulsations,  but  that  in  general  the  average  conditions  of  2,000 
or  3,000  years  ago  were  moister  than  those  of  to-day.  This  is  the  reason  for  adjusting  the 
general  level  of  the  earlier  part  of  the  sequoia  curve  by  means  of  the  variations  in  the  level 
of  the  Caspian  Sea,  and  for  believing  that  the  curve  thus  adjusted  represents  the  approxi¬ 
mate  truth  as  to  the  climatic  pulsations  of  temperate  continental  regions  for  the  past  3,000 
years. 


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SKETCH  5vIAP  OF  A  PART  OF  CENTR^VL  AVIERICA 

SilOWINTG  LOCA'nOI^  OP"  MAYA  RUINS 


CHAPTER  XV. 

THE  PENINSULA  OF  YUCATAN. 

MODERN  GEOGRAPHICAL  CONDITIONS. 

Thus  far  our  attention  has  been  limited  almost  exclusively  to  the  climatic  zones  north 
of  the  trade-wind  belt.  Only  in  one  case  have  we  made  a  slight  excursion  southward  into 
the  torrid  zone  in  southern  Mexico.  There  we  found  that  evidences  of  cHmatic  changes 
are  as  distinct  and  abundant  as  further  north.  Moreover,  as  will  appear  more  fully  below, 
their  periodicity  seems  to  be  the  same  as  that  of  the  temperate  zone,  the  first  half  of  the 
fourteenth  century  having  been  a  wet  period  not  only  in  the  basin  of  Mexico,  but  in  Cali¬ 
fornia  and  in  western  Asia,  while  the  end  of  the  fifteenth  century  was  dry.  This  Mexican 
region,  however,  is  in  many  ways  not  truly  typical  of  the  torrid  zone,  since  it  lies  on  a  high 
plateau  from  5,000  to  7,000  feet  above  the  sea  and  is  cut  off  from  the  neighboring  oceans 
by  high  mountains. 

A  true  test  of  the  torrid  zone  would  demand  the  examination  of  some  lowland  region, 
and  would  be  much  more  valuable  if  it  included  not  only  regions  which,  like  the  Mexican 
plateau,  receive  rain  in  summer  only,  but  also  places  receiving  it  at  all  seasons.  Moreover, 
such  a  place  must  contain  ruins  or  other  traces  of  human  occupation  in  order  to  afford  some 
indication  of  the  dates  of  any  possible  changes.  A  region  of  precisely  this  kind  is  found  in 
the  low,  triangular  area  which  extends  from  latitude  14°  to  22°  in  Central  America.  The 
base  of  the  triangle  extends  about  500  miles  in  a  direction  east  by  south  from  the  Isthmus 
of  Tehuantepec  along  the  Pacific  Coast  and  across  Guatemala  to  the  center  of  Honduras, 
while  the  apex  lies  500  miles  north  of  the  last  point  and  is  the  northwestern  promontory  of 
Yucatan.  The  triangle  is  shown  in  the  accompanying  map.  It  includes  the  Mexican  states 
of  Tabasco  and  Chiapas,  the  entire  peninsula  of  Yucatan,  British  Honduras,  the  two-thirds 
of  Guatemala  lying  north  of  the  Motagua  River,  and  a  considerable  part  of  western 
Honduras.  Here  grew  up  the  civilization  of  the  Mayas,  who  possessed  the  highest  culture 
attained  by  any  American  race  before  the  coming  of  Columbus.  Here  are  found  some  of 
the  most  remarkable  ruins  of  any  portion  of  the  world.  Part  are  located  in  the  dry  regions 
of  northern  Yucatan  and  part  in  the  dense  tropical  forests  where  no  civilized  man  now 
dwells.  Something  is  known  of  their  history,  both  from  a  few  old  records  and  from  the 
ruins  themselves.  Hence  here,  more  perhaps  than  anywhere  else  in  America,  we  have 
an  opportunity  to  test  our  climatic  theories  by  the  twofold  criterion  of  a  new  climatic  zone 
and  a  new  type  of  civilization.  The  results  are  at  first  sight  contradictory  to  those  attained 
elsewhere,  for  the  past  appears  to  have  been  on  the  whole  more  arid  instead  of  more  moist 
than  the  present.  More  carefully  interpreted,  however,  they  are  seen  not  to  be  contra¬ 
dictory  and  to  afford  not  only  a  most  interesting  confirmation  of  the  theory  of  changes  of 
climate,  but  a  valuable  light  upon  the  mechanism  of  such  changes. 

The  best  place  in  which  to  begin  our  main  investigation  into  the  Maya  civilization 
and  its  relation  to  climate  is  the  peninsula  of  Yucatan.  In  view  of  the  importance  of  the 
subject,  and  inasmuch  as  Yucatan  is  a  peculiar  region  and  is  imperfectly  known  to  the 
majority  of  intelligent  readers,  I  shall  describe  some  of  its  more  salient  geographic  featines, 
and  shall  attempt  to  give  an  idea  of  their  relation  to  the  present  habits  and  character  of 
its  Mestizo  and  Maya  population.  This  is  necessary  because  the  most  surprising  feature 
of  the  country — that  is,  the  great  contrast  between  the  past  and  the  present — can  only 
be  understood  on  the  basis  of  a  knowledge  not  only  of  the  wonderful  ruins,  but  of  the 
present  state  of  civilization. 


175 


176 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


One  of  the  first  things  that  strikes  the  geographer  when  he  faces  the  ancient  greatness 
of  Yucatan  is  the  fact  that  the  country  is  highly  isolated,  a  condition  which  tends  notably 
to  retard  rather  than  advance  the  growth  of  civilization.  Toward  the  south  and  east 
the  habitable  portion  of  the  peninsula  is  bounded  by  dense  tropical  forests  which  even  in 
our  day  are  penetrated  neither  by  railroad  nor  road.  The  only  way  to  traverse  them  is 
by  means  of  Indian  trails,  winding  and  crooked,  and  often  coming  blindly  to  an  end.  Even 
these  poor  apologies  for  paths  are  impassable  except  with  the  help  of  a  party  of  natives 
armed  with  big  machetes  for  cutting  the  young  trees  and  lianas  which  grow  up  with  astound¬ 
ing  rapidity.  The  inhabitants  of  the  forests  are  limited  to  a  few  scattered  bands  of  Indians 
in  the  lowest  stages  of  civilization.  Often  the  traveler  may  go  for  days  without  seeing  a 
village  or  even  a  camp.  On  the  other  sides  Yucatan  is  surrounded  by  water,  but  that 
does  not  make  it  accessible.  The  harbors  on  the  east  coast  are  said  to  be  fairly  good,  but 
the  country  back  of  them  is  covered  with  the  same  kind  of  dense  forest  as  the  south,  and 
hence  they  are  almost  useless  as  a  means  of  getting  at  the  important  portions  of  the  country. 
On  the  north  the  coast  is  bordered  by  an  almost  continuous  line  of  sand  bars  and  lagoons. 
Within  the  lagoons  the  water  is  quiet,  and  small  boats  can  sail  easily,  but  unfortunately 
it  is  not  possible  to  go  any  great  distance  without  meeting  barriers  which  force  the  navigator 
to  take  to  the  open  sea.  There  the  waves  raised  by  the  prevaihng  trade  winds,  blowing 
freshly  from  the  northeast,  are  so  high  as  to  make  long  voyages  too  dangerous  to  be  com¬ 
monly  undertaken.  So  far  as  modern  steamers  are  concerned  conditions  are  no  better. 
Like  all  newly  uplifted  coastal  plains  Yucatan  is  bordered  by  very  shallow  seas.  The 
steamers  of  the  Ward  Line,  the  only  one  plying  regularly  to  the  country,  are  forced  to 
anchor  3  miles  or  more  from  land  and  to  send  their  freight  and  passengers  ashore  in  a  tug 
which  pitches  most  disquietingly,  even  in  comparatively  good  weather.  In  bad  weather 
it  is  often  impossible  to  make  any  landing  whatever.  On  the  west  coast,  known  as  Cam¬ 
peche,  conditions  are  somewhat  better  because  of  less  exposure  to  the  winds,  but  the 
difliculties  due  to  shallow  water  are  not  much  different.  Altogether  the  peninsula  of 
Yucatan  is  a  decidedly  inaccessible  region,  and  there  seems  to  be  nothing  in  its  position  to 
account  for  its  past  greatness.  No  great  trade  routes  touch  it,  its  near  neighbors  on 
every  side  are  backward,  and  there  seems  to  be  little  opportunity  for  the  stimulation  which 
comes  by  contact  with  people  of  other  ideas  and  habits. 

The  form  of  the  land  in  Yucatan  is  not  any  more  favorable  than  is  its  location.  As 
has  already  been  implied,  the  northern  part  is  a  coastal  plain  newly  uplifted  from  the 
sea.  For  scores  of  miles  the  general  aspect  of  the  country  is  absolutely  flat.  Near  the 
center  low  hills  rise  to  a  height  of  300  to  400  feet,  and  farther  south  the  relief  becomes 
greater.  The  most  noticeable  ridge,  so  far  as  the  inhabited  portions  of  the  country  are 
concerned,  runs  southwestward  from  a  point  about  30  miles  inland  from  the  northwestern 
corner  of  the  peninsula.  Its  rounded  hills  are  a  prominent  feature  in  the  landscape  as 
looked  at  from  the  plain  to  the  east,  but  are  nowhere  difficult  to  cross;  nevertheless  they 
form  a  genuine  barrier  to  civilization,  largely  because  of  their  relation  to  water-supply, 
rainfall,  and  vegetation. 

Practically  all  of  Yucatan  is  composed  of  soluble  limestone.  This  has  given  rise  to 
one  of  the  most  widely  known  features  of  the  country,  that  is,  its  underground  drainage 
and  ‘‘cenotes”  or  caves.  The  topography  is  almost  universally  of  the  unpropitious  kind 
known  as  “karst.”  The  karst,  however,  is  not  of  the  most  common  type,  for  in  Yucatan 
we  have  to  deal  with  a  level  plain  instead  of  with  a  region  of  considerable  relief.  Because 
of  the  flatness  and  the  porous  nature  of  the  soluble  limestone  such  a  thing  as  a  river  is 
absolutely  unknown.  Not  even  a  brook  is  found  in  the  whole  country,  and  naturally  there 
are  no  valleys.  The  only  break  in  the  flat  monotony  is  afforded  by  innumerable  little 
hillocks  5  to  15  feet  high.  They  lie  in  no  regular  order,  being  merely  the  remnants  which 
happen  to  have  been  left  between  depressions  in  which  a  little  water  gathers  in  the  rainy 


THE  PENINSULA  OF  YUCATAN. 


177 


season.  The  water  stands  in  pools  for  a  while,  and  by  so  doing  tends  to  dissolve  the 
hollows  to  a  deeper  level.  Only  rarely  does  the  water  of  one  hollow  run  over  into  another, 
and  even  then  not  in  sufficient  amounts  to  make  real,  running  streams.  Such  being  the 
case,  the  drainage  of  the  country  is  confined  to  underground  channels  which  exist  in  large 
numbers.  Often  the  concealed  waters  dissolve  large  caves  whose  tops,  in  many  cases, 
have  fallen  in,  exposing  the  water  at  a  depth  of  anywhere  from  20  to  100  feet,  and  thus 
giving  rise  to  the  openings  known  as  “cenotes.”  These  broken-down  caves  are  highly  im¬ 
portant  to  the  inhabitants,  for  they  are  almost  the  only  places  where  a  permanent  supply  of 
water  is  naturally  obtainable  throughout  the  whole  year.  At  the  time  of  the  coming  of 
the  Spaniards  all  the  native  inhabitants,  the  Maya  Indians,  as  they  are  called,  are  said 
to  have  been  clustered  around  them  or  else  around  the  few  “aguadas”  or  natural  hollows 
which  contain  water  during  most  of  the  year,  although,  unlike  the  cenotes,  they  sometimes 
dry  up.  Having  no  iron  tools,  the  primitive  Mayas  were  unable  to  dig  wells,  although 
to-day  these  can  be  dug  almost  everywhere  with  full  assurance  of  strildng  an  abundant  and 
unfailing  supply  of  water.  The  only  difficulty  is  that  in  the  hilly  regions  the  wells  have 
to  be  sunk  to  a  depth  of  from  100  to  200  feet,  and  the  labor  involved  is  sufficient  in  many 
cases  to  prevent  the  inefficient  people  of  the  tropics  from  making  the  attempt.  Where 
ground  water  hes  at  a  depth  of  only  20  or  30  feet,  as  in  most  parts  of  the  plain,  wells  are 
numerous.  In  many  cases  the  water  is  raised  by  windmills,  which  seem  to  rise  like  a  forest 
when  one  looks  from  a  distance  at  such  a  town  as  Merida,  the  capital.  During  recent 
years,  when  Yucatan  has  grown  rich  from  the  henequen  or  sisal  fiber  industry,  pumps  run 
by  gasohne  or  steam  have  in  many  places  appeared. 

Climatically,  as  well  as  in  other  ways,  Yucatan  is  relatively  simple.  It  lies  in  the 
trade-wind  belt  from  19  to  21  degrees  north  of  the  equator.  In  winter  the  brisk  winds 
from  the  ocean  pass  over  the  land  without  giving  up  much  moisture.  The  sky  is  clear  a 
large  part  of  the  time,  and  although  some  rain  falls  in  every  month  the  amount  in  the 
northern  parts  of  the  country  is  insignificant.  Farther  south,  however,  or  where  the  hills 
begin  to  rise,  the  rainfall  increases  rapidly,  and  showers  are  frequent.  The  temperature 
in  winter  is  agreeable,  being  rarely  extremely  w'arm  and  never  cold  according  to  the  ideas 
of  people  from  the  north.  In  spite  of  this  there  is  considerable  variety,  especially  when 
the  so-called  northers  blow.  These  appear  to  be  connected  with  the  cyclonic  storms  of 
the  United  States.  The  wind  blows  violently  from  the  north  and  reduces  the  tempera¬ 
ture  to  the  lowest  points  ever  reached.  The  minimum,  however,  is  rarely  below  10°  C. 
(50°  F.),  while  the  maximum,  even  in  winter,  is  usually  above  30°  C.  (86°  F.),  and  may 
rise  above  40°  C.  by  the  end  of  March.  In  summer,  as  might  be  expected  in  this  latitude, 
the  zone  of  equatorial  rains  exerts  its  accustomed  influence  and  gives  rise  to  heavy  tropical 
showers.  How  greatly  the  summer  rainfall  exceeds  that  of  winter  may  be  seen  from 
table  9,  which  gives  the  average  monthly  rainfall  (in  inches)  for  the  15  years  from  1896 
to  1910  inclusive  at  Merida. 

Table  9. 


Month. 

Ilainfall. 

Month. 

Rainfall. 

0.88 

July . 

4.90 

0.68  1 

8.48 

0.58 

4.46 

0.74 

3.04 

1.70 

1.94 

5.61 

1.36 

Total . 

34.37 

The  seasonal  variation  of  rainfall  is  no  more  striking  than  its  variation  from  region 
to  region.  In  the  north  the  rainfall  is  slight,  being  at  a  minimum  on  the  coast  in  the 
neighborhood  of  Progreso.  Here,  in  1911,  the  only  year  for  which  statistics  are  at  hand, 
13 


178 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  precipitation  amounted  to  13.5  inches.  From  15  to  20  miles  inland,  at  Merida,  and 
at  Motul  and  Temax  which  lie  farther  east,  the  precipitation  for  the  same  year  was  35.7, 
37.6,  and  34.8  inches,  respectively.  Still  farther  inland,  at  places  varying  from  30  to  90 
miles  from  the  coast,  the  figures  are  as  follows :  Izamal,  40  miles  due  east  of  Merida,  49.2 
inches;  Espita,  nearly  as  much  again  to  the  east,  48.7  inches;  Tekax,  50  miles  south-south¬ 
east  of  Merida,  53.3  inches;  and  Peto,  about  30  miles  southeast  of  Tekax  but  not  so  much 
among  the  hills,  47.7  inches.  Finally,  to  the  east  and  south  of  the  places  already  mentioned 
we  find  an  area  of  still  larger  rainfall,  exemplified  by  Valladolid,  which  lies  100  miles  east- 
southeast  of  Merida  and  about  50  miles  from  the  Caribbean  Sea.  It  had  a  rainfall  of 
66.8  inches  in  1911,  Southward  beyond  this  point,  to  judge  from  the  vegetation,  the 
precipitation  becomes  still  greater.  The  cause  of  the  variation  in  rainfall  is  twofold.  In 
the  first  place,  the  presence  of  hills  in  the  south  and  southwest  on  the  one  hand,  and  the 
abundance  of  easterly  oceanic  winds  on  the  east  coast,  give  those  regions  much  rain.  In 
the  second  place,  we  are  here  near  the  edge  of  the  area  reached  by  the  zone  of  subequatorial 
rains.  Hence  the  amount  of  these  rains  increases  rapidly  toward  the  south. 

With  such  marked  changes  in  the  amount  of  rainfall  from  place  to  place,  it  is  evident 
that  the  vegetation  must  vary  greatly,  and  that  this  fact  in  turn  must  profoundly  affect 
the  conditions  of  human  fife.  The  botanical  works  commonly  emphasize  the  distinction 
between  tropical  bush,  tropical  jimgle,  and  tropical  forest.  Nevertheless,  in  the  mind  of 
the  average  geographer,  if  I  may  judge  from  my  own  experience,  and  still  more  in  the 
mind  of  the  layman,  the  distinction  often  lacks  sharpness.  There  is  a  still  greater  lack  of 
appreciation  of  the  significance  of  these  three  types  in  their  effect  on  man.  In  Yucatan 
bush,  forest,  and  jungle  lie  so  close  together  that  they  can  readily  be  compared.  In 
the  center  of  Yucatan  fies  a  long  narrow  lake  called  Kichankanab,  one  of  several  which 
occupy  hollows  in  the  limestone  of  the  southerly,  more  hilly  portion  of  the  peninsula. 
It  is  located  about  100  miles  east  of  Campeche,  100  west  of  the  Caribbean  Sea,  and  100 
south  of  the  northern  shore  of  the  peninsula.  If  lines  be  drawn  northeastward  and  north¬ 
westward  from  the  lake  to  the  corners  of  the  peninsula  they  will  include  approximately  the 
entire  area  of  the  Mexican  administrative  province  of  Yucatan,  which  comprises  only 
about  one-fifth  of  the  whole  peninsula.  This  small  fifth  of  the  country,  together  with  a 
strip  of  the  west  coast  reaching  down  toward  Campeche,  comprises  the  bush-covered 
portion,  while  the  rest  is  covered  with  jungle  or  genuine  forest.  The  western  boundary  of 
the  bush  area  is  nearly  coincident  with  the  small  range  of  hills  already  mentioned  as  the 
most  noticeable  feature  of  the  relief.  The  eastern  boundary  appears  to  be  less  distinct, 
although  I  have  not  seen  it  and  can  not  speak  with  assurance.  Where  bush  prevails 
the  rainfall  seems  not  to  exceed  30  or  40  inches,  while  in  the  forested  area  it  rises  far 
higher.  How  great  it  is  we  do  not  know,  for  Valladolid  with  nearly  67  inches  in  1911  is 
the  only  station  whose  figures  are  obtainable,  and  it  lies  on  the  relatively  dry  edge  of  the 
forest,  not  in  its  moist  interior. 

The  distinction  between  bush,  jungle,  and  forest  is  simple.  Large  trees  demand  that  the 
soil  in  which  they  stand  shall  not  be  dry  for  any  great  length  of  time  during  the  growing 
season.  Inasmuch  as  the  growing  season  may  last  the  entire  year  in  the  tropics,  large 
trees  will  not  flourish  in  such  a  way  as  to  form  dense  forests  unless  abundant  rain  falls  at 
most  seasons,  although  they  may  grow  sporadically  here  and  there.  Smaller,  more  drought- 
resistant  species,  however,  as  well  as  bushes,  are  much  less  exacting  in  their  demands  for 
moisture.  Some  of  them  will  grow  almost  anywhere  provided  that  the  ground  is  well 
moistened  for  2  or  3  months  during  some  portion  of  the  year  and  there  is  sufficient  warmth. 
In  regions  like  Progreso,  on  the  north  coast,  where  the  rainfall  is  only  10  to  15  inches, 
concentrated  largely  in  the  summer,  the  long  dry  period  of  winter  prevents  the  growth  of 
anything  except  small  bushes  6  to  8  feet  high;  these,  however,  thrive  in  abundance,  so  that 
the  country  is  well  covered  with  vegetation  and  is  everywhere  bright  green  in  summer. 


THE  PENINSULA  OF  YUCATAN. 


179 


In  the  dry  winter,  however,  the  leaves  fall  off  and  the  landscape  would  be  quite  like 
that  of  a  thick,  bushy  pasture  in  the  United  States  at  the  same  season,  were  it  not  that 
in  the  late  winter  and  early  spring  some  of  the  bushes  bear  brilliant  red,  yellow,  or  white 
flowers.  As  one  goes  inland  from  the  north  coast  to  regions  of  greater  rainfall  such  as 
Tekax  and  Peto,  bush  begins  to  give  place  to  jungle.  The  size  of  the  shrubby  growths 
increases;  small  trees,  20  feet  high,  become  numerous;  a  considerable  number  of  trees 
rise  to  a  height  of  30  or  40  feet,  and  some  are  much  higher.  In  spite  of  this,  however, 
neither  the  dense  underbrush  nor  the  larger  trees  suggest  the  deep,  somber  forest.  Small 
growths  not  over  20  feet  high  and  with  stems  only  3  or  4  inches  in  diameter  predominate. 
Their  aspect  is  like  that  of  a  second  growth  of  timber  in  the  northern  United  States,  15  or 
20  years  after  the  cutting  of  the  original  forest.  A  few  bushes  and  even  an  occasional 
tree  of  some  special  species  may  remain  green  throughout  the  year,  but  during  the  dry 
season  most  become  as  bare  as  northern  trees.  With  every  mile  that  one  advances  into 
the  interior,  however,  the  jungle  becomes  more  permanently  green,  the  density  of  the  lower 
growths  increases,  and  the  proportion  of  genuine  trees  becomes  greater,  until  finally  jungle 
gives  place  to  genuine  forest. 

From  the  jungle  to  the  forest  the  transition  is  rapid.  A  day’s  ride  on  horseback  is 
often  sufficient  to  take  one  from  a  well-developed  sample  of  one  to  an  almost  equally 
well-developed  sample  of  the  other.  The  forest  is  of  the  kind  whose  descriptions  we  are 
so  familiar  with.  Many  of  the  trees  remain  green  throughout  the  year.  They  rise  to 
heights  of  50  to  60  feet  even  on  the  borders  of  their  province,  and  at  the  top  form  a  canopy 
so  that  the  ground  is  shady  most  of  the  time.  Until  9  or  10  o’clock  in  the  morning  the  rays 
of  the  sun,  even  in  the  drier  part  of  the  year  when  a  portion  of  the  leaves  have  fallen, 
scarcely  reach  the  ground.  Even  at  high  noon  the  sunlight  straggles  through  only  in  small 
patches.  Long,  sinuous  hanas,  often  queerly  braided,  hang  down  from  the  trees ;  epiphytes 
and  various  other  parasitic  growths  add  their  strange  greens  and  reds  to  the  continually 
varied  complex  of  plants.  Young  palms  grow  up  almost  in  a  day,  and  block  a  trail  which 
was  passable  only  a  few  months  before.  Wherever  the  death  of  old  trees  forms  an  opening, 
a  hundred  seedhngs  begin  a  fierce  race  to  reach  the  light  and  strangle  their  competitors. 
Everywhere  the  dominant  note  is  intensely  vigorous  life,  rapid  growth,  and  quick  decay, 
as  befits  the  warm,  moist  air  which  rarely  varies  and  never  is  so  cold  or  dry  as  seriously  to 
interfere  with  the  development  of  plants,  even  of  the  most  highly  sensitive  types. 

Before  passing  on  to  discuss  the  effect  of  the  vegetation  and  of  other  conditions  on  man, 
a  word  as  to  the  relation  of  the  karst  phenomena  to  vegetation.  It  is  sometimes  stated 
that  the  paucity  or  rather  the  small  size  and  xerophilous  character  of  the  vegetation  of 
northern  Yucatan  is  largely  due  to  the  dryness  of  the  soil  occasioned  by  the  draining  away 
of  the  water  through  the  caves  and  underground  channels.  Undoubtedly  this  is  an  im¬ 
portant  factor,  but  it  may  not  be  so  important  as  is  generally  assumed.  In  no  country 
where  the  growing  season  is  at  all  warm  can  a  rainfall  of  10  to  15  inches  produce  anything 
except  vegetation  of  a  distinctly  arid  type.  In  a  country  so  warm  as  Yucatan  30  or  40 
inches  is  by  no  means  a  large  rainfall,  and  even  if  none  of  it  were  lost  in  the  karst,  the 
country  would  still  be  relatively  arid  because  of  the  great  evaporation,  especially  during 
the  long  dry  season.  Still  farther  south  not  only  on  the  edges,  but  actually  within  the  limits 
of  the  genuine  forest,  karst  phenomena  seem  to  be  as  marked  as  near  the  northern  coast, 
but  this  does  not  prevent  the  growth  of  the  rankest  kind  of  vegetation.  It  seems,  therefore, 
that  while  the  karsted  character  of  the  country  plays  a  part  in  preventing  the  growth  of 
vegetation,  it  is  by  no  means  so  important  as  the  relatively  small  amount  of  precipitation. 

To  turn  now  from  the  physical  aspects  of  Yucatan  to  its  people,  the  inhabitants  consist 
of  every  gradation  from  pure  Indians  to  pure  Spaniards.  The  forests  and  the  remoter 
villages  are  occupied  by  pure  Indians  of  the  Maya  stock;  the  small  towns  and  the  less 
remote  villages  are  peopled  by  a  mixed  race  of  Mestizos,  in  which  the  Indian  element 


180 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


predominates,  while  in  the  larger  towns  and  their  environs  the  proportion  of  Spanish  blood 
steadily  rises.  The  degree  of  energy  and  initiative  seems  to  vary  in  response  to  two 
factors,  namely,  the  amount  of  Spanish  blood  and  the  length  of  time  that  a  given  stock  has 
been  in  the  country.  As  this  point  bears  on  our  interpretation  of  the  ruins  a  httle  ampli¬ 
fication  is  needed.  The  pure  Indian  is  a  quiet,  slow  being,  inoffensive  and  retiring  unless 
abused.  He  seems  never  to  work  unless  compelled.  As  for  storing  up  anything  for  the 
future,  the  thought  seems  scarcely  to  enter  his  head.  If  he  has  enough  to  eat,  he  simply 
sits  still  and  enjoys  life  until  hunger  again  arouses  him  to  activity.  His  wants  are  few  and 
easily  supplied.  His  agriculture  begins  by  cutting  the  small  growths  of  the  bush,  or  jungle, 
girdling  the  larger  trees,  leaving  the  brush  to  dry  during  the  season  of  little  rain,  and  finally 
burning  it  off.  Then  he  goes  around  with  a  pointed  stick,  making  holes  into  which  he 
drops  corn,  pumpkin  seed,  beans,  and  the  seeds  of  one  or  two  other  vegetables.  The  corn 
is  his  chief  reliance.  When  the  crop  is  ripe,  he  has  no  thought  of  gathering  it  all  at  once 
and  storing  it  away  safely,  perhaps  in  the  form  of  flour  or  at  least  shelled.  His  method 
is  to  go  out  to  the  field  in  the  early  part  of  the  dry  season  after  the  corn  is  well  ripe,  and 
half  break  each  stalk  in  the  middle  so  that  it  is  bent  over  and  the  ears  point  downward. 
Little  by  little  he  picks  what  ears  he  needs  for  daily  use,  caring  nothing  that  insects,  birds, 
and  beasts  are  also  eating  what  they  need.  He  knows  that  a  quarter  or  a  third  of  the  ears 
may  be  spoiled,  but  so  long  as  there  are  some  for  him,  he  cares  little.  The  only  thing  that 
ultimately  stirs  him  up  to  gather  the  remainder  of  the  crop  is  the  end  of  the  dry  season. 
Before  the  rains  come  he  knows  that  he  must  harvest  his  crop  and  plant  more  seed  or 
else  he  will  starve.  Therefore  he  arouses  himself  for  the  one  period  of  effort  during  the 
year.  He  is  hardly  to  be  blamed  for  his  apparent  laziness.  He  certainly  is  lazy  according 
to  our  standards,  but  he  has  little  to  stimulate  him,  and  it  is  easy  to  get  a  living  without 
much  work.  In  good  qualities,  however,  he  is  by  no  means  lacking.  He  is  extremely 
courteous,  and  according  to  all  accounts  he  excels  in  both  honesty  and  morality. 

As  the  amount  of  Spanish  blood  in  the  people  of  Yucatan  increases,  their  energy  and 
resourcefulness  increase.  They  also  become  more  light-hearted  and  gaj"  than  the  silent, 
sober  Indians,  but  at  the  same  time  honesty  and  morality  are  said  to  decrease  markedly. 
All  classes  of  people,  however,  are  decidedly  slow  compared  with  Americans  or  people  of 
western  Europe.  In  this  connection  a  fact  as  to  the  Spaniards  is  worth  recording.  In 
Yucatan,  as  well  as  in  other  parts  of  Mexico,  there  is  a  surprisingly  large  number  of  recent 
Spanish  immigrants.  According  to  almost  universal  testimony  these  immigrants  are 
better  workers  than  the  corresponding  class  of  natives,  no  matter  whether  the  natives  are 
Indians,  Mestizos,  or  Spaniards  who  have  been  in  the  country  a  generation  or  two.  Some¬ 
thing  in  the  new  environments  seems  to  make  people  slow.  In  part  it  maj’-  be  contact  with 
an  inferior  race,  but  more  probably  it  is  a  climatic  matter.  Doubtless  the  heat  has  much 
to  do  with  it,  but  there  seems  ground  for  believing  that  the  uniformity  of  the  temperature 
is  quite  as  harmful  as  its  degree. 

The  distribution  of  the  human  inhabitants  of  Yucatan  is  very  uneven.  Practically 
all  of  the  400,000  who  inhabit  the  peninsula  live  in  the  bush  region,  that  is,  Yucatan 
proper  and  the  coastal  strip  north  of  Campeche.  The  rest  of  the  country,  comprising 
most  of  the  province  of  Campeche  and  the  federal  district  known  as  Quintana  Roo,  contains 
only  a  few  wild  Indians  numbering  4,000  to  5,000.  The  reason  is  not  far  to  seek;  the 
tropical  forest  is  too  dense  for  them  to  conquer.  This  matter  deserves  emphasis,  for  it 
seems  to  be  more  important  than  is  generally  realized,  and  it  may  have  a  close  bearing  upon 
the  problem  of  changes  of  climate.  The  descriptions  of  tropical  forests  are  usually  couched 
in  such  indefinite  terms  that  it  is  hard  to  tell  whether  a  given  area  in  its  pristine  condition 
would  be  covered  with  jungle  or  forest.  Practically  all  of  the  tropical  regions,  however, 
where  the  natives  are  at  present  in  such  a  state  of  civilization  that  they  live  permanently 
in  good-sized  villages  and  depend  primarily  upon  agriculture  for  a  living,  seem  to  be  located 


THE  PENINSULA  OF  YUCATAN. 


181 


where  the  prevalent  natural  growth  is  of  the  types  which  we  have  defined  as  bush  and 
jungle.  In  such  regions  it  is  possible  for  a  comparatively  inefficient  people  to  get  a  living  by 
agriculture.  The  small  trees  or  bushes  with  a  diameter  of  5  inches  or  less  can  readily  be 
hacked  down  with  almost  any  kind  of  heavy  knife,  while  the  larger  ones  can  be  girdled 
by  cutting  off  the  bark  near  the  base,  and  will  soon  die.  Provided  this  is  done  during 
the  earlier  part  of  the  dry  season,  which  is  characteristic  of  all  tropical  regions  where 
bush  or  jungle  prevails,  the  bushes  and  perhaps  some  of  the  girdled  trees  will  be  dry 
enough  to  burn  before  the  rains  come  again.  Hence  it  is  a  comparatively  simple  matter  to 
clear  a  tract  and  plant  it.  If  some  of  the  few  larger  trees  of  the  jungle  remain  standing, 
little  harm  is  done. 

In  the  true  forest  the  case  is  quite  different.  In  the  first  place  the  trees  are  large,  the 
majority  having  trunks  at  least  a  foot  in  diameter  and  many  of  them  much  more.  More¬ 
over,  their  wood  is  frequently  hard.  Hence  it  is  difficult  to  cut  them  down.  Only  people 
of  great  energy  are  capable  of  doing  so  on  any  large  scale.  If  the  much  easier  process  of 
girdling  is  resorted  to,  the  trees  will  die  in  course  of  time,  and  it  might  seem  as  if  even  the 
inefficient  people  of  the  tropics  could  thus  clear  large  areas.  Unfortunately  another 
difficulty  arises,  one  which  is  serious  where  the  trees  are  actually  cut,  and  much  more  so 
where  they  are  girdled.  The  chmate  of  the  true  tropical  forests  is  so  uniformly  moist 
that,  even  when  trees  have  been  felled,  it  takes  a  long  time  for  them  to  become  dry  enough 
to  burn.  Moreover,  while  they  are  drying,  new  vegetation  at  once  begins  to  sprout,  and 
by  the  time  the  trees  are  ready  to  burn  the  new  growth  is  so  large  that  it  prevents  the 
fire  from  spreading  from  tree  to  tree.  That  this  is  so  is  evident  from  the  fact  that  even  in 
the  jungle  region  the  fires  which  are  lighted  every  year  in  the  spring  to  burn  off  the  corn¬ 
stalks  rarely  spread  to  any  great  distance  in  the  uncut  jungle.  The  speed  with  which 
plants  grow  in  the  tropics  is  far  more  than  we  commonly  realize.  One  day  on  the  southern 
edge  of  the  jungle,  near  the  forest  but  well  out  of  it,  my  guide  remarked  that  the  land 
over  which  we  were  passing  had  been  cultivated  3  years  before.  Already  the  bushes  were 
15  feet  high.  In  the  heart  of  the  forest  the  growth  is  even  faster.  Hence  the  very  rankness 
of  the  growth  of  vegetation  is  one  of  the  primary  reasons  why  man  has  never  yet  really 
mastered  any  considerable  area  where  genuine  tropical  forests  prevail. 

Other  reasons  for  this  result  also  exist.  Malarial  fevers  are  much  worse  in  the  forest 
than  in  the  jungle,  and  are  worse  in  the  jungle  than  in  the  bush.  The  natives  are  said  to 
be  immune  to  such  fevers,  but  modern  research  throws  considerable  doubt  on  this.  The 
adults  are  immune,  but  how  about  the  children?  The  researches  of  Sir  Ronald  Ross  and 
of  the  School  of  Tropical  Medicine  at  Liverpool  have  shown  that  in  countries  badly  infested 
with  malaria  adults  do  not  suffer  much  from  the  disease,  but  that  nearly  half  of  the  children 
have  it  year  after  year  during  childhood,  and  a  large  number  bear  its  marks  through  life 
in  the  form  of  enlarged  spleens  and  other  injurious  alterations  of  the  organs.  Every  gener¬ 
ation  is  apparently  distinctly  weakened  by  the  diseases  through  which  it  passes  in  child¬ 
hood.  Similarly,  in  places  such  as  Merida,  where  yellow  fever  is  endemic,  it  is  said  that  the 
natives  never  suffer  and  that  epidemics  break  out  only  when  newcomers  arrive  from  outside. 
Many  physicians  now  think,  however,  that  large  numbers  of  the  children  have  the  fever 
in  infancy.  Those  who  die  are  supposed  to  have  suffered  from  other  infant  complaints, 
while  those  who  recover  are  of  course  immune.  In  the  case  of  yellow  fever  the  after  effects 
are  generally  not  serious,  but  in  the  case  of  malarial  fevers,  especially  such  forms  as  prevail 
in  the  tropics,  the  debilitating  results  often  last  through  life.  Thus  it  may  be  that  the 
severe  fevers  of  the  forests,  attacking  the  children  and  killing  many  of  them,  leave  the 
remainder  permanently  weakened  and  incapacitated  for  the  work  of  forwarding  civilization 
in  their  hard  surroundings. 

In  general,  so  far  as  the  effects  of  climate  upon  human  efficiency  are  concerned,  there 
seems  to  be  a  curious  contradiction  between  equatorial  and  non-equatorial  regions.  In  the 


182 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


equatorial  regions  a  relative  lack  of  rain  seems  to  be  beneficial,  while  elsewhere  it  is  usually 
detrimental.  At  any  rate  the  most  progressive  parts  of  the  tropics  appear  in  general  to 
be  comparatively  dry,  while  the  most  progressive  countries  of  the  temperate  zone  are  in 
general  located  in  regions  of  comparative  moisture,  or  else  have  been  recently  settled  by 
people  from  regions  of  that  sort.  The  dryness  of  the  little  strip  of  northern  Yucatan  where 
civilization  now  centers  seems  to  be  almost  the  only  feature  of  the  geographic  environment 
which  is  distinctly  favorable. 

THE  ANCIENT  MAYA  CIVILIZATION. 

Among  the  noteworthy  characteristics  of  Yucatan,  we  have  seen  that  none  is  more 
interesting  than  the  contrast  between  the  civilization  of  the  past  and  of  the  present.  In 
spite  of  the  slowness  and  inefficiency  of  the  inhabitants  as  compared  with  the  people  of 
Europe,  Yucatan  compares  favorably  with  other  tropical  lands,  and  enthusiastic  travelers 
have  sometimes  claimed  that  Merida  is  the  richest  city  in  the  world  in  proportion  to  its 
size.  That  the  country  has  an  uncommonly  prosperous  air  is  certainly  true.  This  is 
partly  due  to  the  fact  that  the  henequen  or  sisal  fiber  industry  has  proved  most  lucrative, 
especially  during  the  period  when  the  supply  of  Manila  hemp,  its  chief  rival,  was  cut  off 
by  the  Spanish-American  war.  Without  the  sisal  Yucatan  would  rank  well  among  the 
countries  of  the  torrid  zone,  but  would  by  no  means  be  so  conspicuous  as  is  now  the  case. 
The  prosperity  of  to-day,  however,  is  but  a  slight  incident  compared  with  that  of  the  past. 
The  present  prosperity  is  in  danger  of  being  ephemeral.  Much  of  it  would  vanish  if 
another  fiber  as  good  as  henequen  should  be  discovered  in  places  where  it  could  be  raised 
more  cheaply  than  in  Yucatan;  and  even  if  the  prosperity  should  last,  it  is  an  extraneous 
matter.  It  is  due  to  the  demands  of  the  United  States  and  other  countries,  it  is  fostered  by 
their  steamship  lines,  and  its  benefits  are  chiefly  reaped  not  by  the  Indians  and  Mestizos, 
but  by  people  of  Spanish  blood,  most  of  whom  have  not  been  in  the  country  more  than  a 
generation  or  two.  Moreover,  its  effect  upon  the  country  as  a  whole  is  slight  outside  of 
Merida.  It  has  not  stimulated  the  native  population  to  any  special  activity,  nor  has  it 
caused  the  construction  of  buildings  whose  ruins  will  endure  to  commemorate  it.  In 
Merida,  to  be  sure,  it  has  led  to  the  erection  of  many  stone  buildings  which  will  give  to  the 
archeologist  of  the  future  an  idea  of  considerable  prosperity,  but  there  the  matter  ends. 
If  the  present  inhabitants  were  to  be  suddenly  removed  and  the  country  left  desolate, 
the  archeologist  of  3000  a.  d.  would  find  few  traces  of  the  present  civilization  except  small 
heaps  of  stones  in  the  country  districts,  and  the  remnants  of  a  number  of  mediocre  buildings 
in  the  little  provincial  capital.  There  would  be  nothing  to  arouse  his  enthusiasm;  the  ruins 
of  almost  any  county  seat  of  60,000  inhabitants  in  the  United  States  or  northwestern 
Europe  would  present  far  greater  evidences  of  a  high  civilization.  It  would  be  almost 
obtrusively  evident  that  Merida  in  its  prime  was  merely  a  feeble  imitation  of  a  civilization 
whose  real  center  was  far  away. 

Turning  now  to  the  past,  we  find  an  entirely  opposite  state  of  affairs.  The  ruins  of 
scores  of  superb  temples  and  other  structures  scattered  in  the  bush,  jungle,  and  forest  of 
all  parts  of  Yucatan  and  the  adjacent  Maya  lands  proclaim  unmistakably  that  the  country 
once  possessed  a  civilization  which,  for  its  period  and  continent,  was  the  highest  in  existence. 
Here,  not  elsewhere,  was  the  center,  and  here  that  civilization  not  only  developed  but 
persisted  for  century  after  century.  The  ruins,  while  not  a  tithe  as  beautiful  as  those  of 
Athens,  make  upon  the  traveler  the  same  impression  of  wonderful  power  and  originality 
in  their  builders,  the  same  sense  of  having  been  built  by  a  people  who  were  masters  of  their 
art  and  who  gloried  in  their  skill.  Any  detailed  description  of  the  ruins  would  be  out  of 
place  in  this  volume,  but  a  little  discussion  of  them  is  needed  in  order  to  show  how  high  the 
ancient  civilization  actually  was  and  wherein  lay  some  of  its  chief  elements  of  greatness. 


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HUNTINGTON 


PLATE  8 


A.  Market-place  in  Yucatan,  showing  the  best  modern  architecture. 

B.  Typical  house  in  Yucatan. 

C.  Archway  at  Labna. 

D.  Farmer’s  hut  in  the  midst  of  Labna,  one  of  the  greatest  ancient  cities;  corn  cobs  on  the  left,  pumpkins 

on  right,  corn  stalks  in  foreground,  and  jungle  of  a  few  year's  growth  in  background, 

E.  Rums  of  Chac-multun. 


THE  PENINSULA  OF  YUCATAN. 


183 


Unless  these  things  are  appreciated,  we  can  not  form  a  fair  judgment  as  to  why  the  past 
was  so  different  from  the  present. 

One  of  the  most  impressive  features  of  the  ruins  is  the  abundance,  size,  and  sohdity  of 
the  various  structures.  For  instance,  at  Chichen  Itza,  where  within  a  radius  of  25  miles 
on  either  side  there  are  probably  to-day  not  5,000  people,  there  was  once  a  vast  city. 
Mr.  E.  H.  Thompson,  whose  home  has  for  years  been  directly  among  the  ruins,  says  that 
the  area  of  dense  urban  population  was  at  least  6  miles  square;  that  is,  it  comprised  no 
less  than  36  square  miles,  while  beyond  it  lay  abundant  suburbs.  Such  a  city,  even  if  it 
had  but  two  families  to  the  acre,  would  have  contained  fully  230,000  people;  whereas  all 
Yucatan  to-day  has  a  population  of  only  a  little  over  300,000.  Chichen  Itza,  however, 
by  no  means  stands  alone.  Ninety-two  ruins  are  known,  according  to  Mr.  Thompson, 
and  many  of  them  must  have  been  towns  of  large  size.  Otherwise  they  could  not  possibly 
have  possessed  the  wealth  and  surplus  labor  requisite  for  the  construction  of  temples  such 
as  that  of  Labna,  375  feet  long  and  3  stories  high.  Yet  Labna  is  only  one  of  a  score  of 
notable  ruins  lying  close  together  within  15  or  20  miles  of  Uxmal.  All  the  ruins  are  mas¬ 
sively  constructed  with  carefully  dressed  stones  on  the  surface  and  rubble  of  uncut  stones 
and  mortar  filling  the  spaces  between  the  flat-topped,  false  arches  and  holding  them  solid. 
So  firm  is  the  construction,  that  even  in  some  cases,  such  as  Uxmal,  where  the  lintels  were 
made  of  zapote  timber,  which  has  rotted  in  spite  of  its  extraordinary  durability,  the  walls 
have  fallen  but  slightly. 

The  size  and  massiveness  of  the  Yucatecan  ruins  are  no  more  remarkable  than  are  the 
originality,  variety,  and  delicacy  displayed  in  their  adornment.  The  intricate  patterns 
carved  upon  the  fagades  of  scores  of  temples  and  palaces  vary  most  interestingly.  In 
some  places  one  finds  massive  geometrical  designs  which  are  made  of  rectangular  stones  jut¬ 
ting  out  from  the  face  of  some  lofty  wall.  Elsewhere  large  numbers  of  columns  are  seen, 
some  being  small  and  purely  ornamental,  and  others  large  enough  to  form  colonnades. 
Still  another  type  of  adornment  consists  of  huge  stone  serpents,  strange  forms  of  bird 
and  beast,  or  grinning,  distorted  human  heads  set  with  great  teeth.  And  lastly,  the  cul¬ 
mination  of  the  ancient  Yucatecan  art  is  reached  in  delicately  modeled  busts,  which  can 
bear  comparison  with  the  work  of  any  people  except  the  Greeks  and  those  who  have 
learned  from  them.  At  Kabah,  a  ruin  rarely  visited  by  foreigners,  two  heads,  lately 
exhumed,  stand  side  by  side.  The  plaited  hair  of  these  two  figures  and  the  high  tiaras  are 
not  particularly  remarkable,  although  carefully  executed.  The  thing  which  rivets  attention 
is  the  skillfully  modeled  features,  the  hooked  noses,  Jewish  in  outline,  but  with  wider, 
more  tropical  nostrils;  the  curved  lips  and  the  sparse,  drooping  mustaches.  The  eyes, 
too,  are  noticeable,  but  before  one  has  time  to  analyze  them,  his  attention  is  diverted  by 
the  curious  chain  which  in  each  case  encircles  the  left  eye,  falls  down  over  the  cheek,  and  is 
brought  up  to  the  chin.  From  the  statues  I  turned  to  our  guide,  a  Maya  Indian,  and  saw 
the  same  features  repeated  in  brown,  living  flesh.  Our  Maya  driver  also  had  the  same 
hooked  nose,  wide  nostrils,  and  drooping  mustache.  The  chief  difference  was  in  a  lesser 
curvature  of  the  mouth.  So  well  did  the  old  masters  work,  1,000  or  2,000  years  ago,  that 
although  we  know  nothing  of  the  origin  or  affinities  of  the  race  to  which  they  belonged,  we 
can  at  least  affirm  that,  in  spite  of  mixture  with  foreign  elements,  their  blood  still  flows  in 
Yucatan. 

I  dwell  on  these  matters  in  order  to  emphasize  the  fact  that  the  ancient  Yucatecos  were 
a  highly  civilized  and  prosperous  race;  they  were  blessed  with  a  large  amount  of  surplus 
wealth  which  they  could  use  to  support  the  architects,  sculptors,  painters,  and  engineers 
who  superintended  the  building  of  the  temples  and  evolved  the  myriads  of  ideas  which 
were  everywhere  brought  to  fruition.  And  there  was  also  wealth  to  support  the  thousands 
upon  thousands  of  workmen  who  quarried  the  rock,  carried  it  to  the  buildings,  and  hewed 
it  to  the  exact  dimensions  demanded  by  the  plans  of  the  masters.  Other  workmen  burned 


184 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  lime  with  which  an  army  of  masons  cemented  the  hewn  stones  or  filled  in  the  great 
spaces  of  rubble  between  the  arches.  Elsewhere  men  were  toiling  to  build  and  repair  the 
cisterns  or  reservoirs  which  enabled  a  large  population  to  dwell  in  this  riverless,  springless 
land  of  underground  drainage.  Aside  from  the  throngs  engaged  in  work  of  a  semi-public 
character,  still  larger  bodies  of  men  must  have  been  busily  tilling  the  soil.  Each  man 
raised  more  food  than  his  own  family  consumed.  To-day,  as  we  have  seen,  the  Indian 
farmer  rarely  raises  or  harvests  more  than  enough  for  his  immediate  needs,  and  his  wife 
literally  can  not  comprehend  the  value  of  grinding  to-morrow’s  corn  to-day  or  yesterday. 
The  hand-to-mouth  methods  of  to-day  can  scarcely  have  prevailed  in  the  past,  for  at  that 
time  there  must  always  have  been  a  large  surplus  supply  of  food  which  by  barter  or  taxation 
was  available  as  a  store  to  support  the  non-agricultural  artisans  and  laborers. 

At  what  time  these  conditions  ceased  to  prevail  no  man  can  tell  exactly.  When  the 
Spaniards  came  to  Yucatan  early  in  the  sixteenth  century,  the  Mayas  were  much  as  they 
are  to-day,  a  slow,  mild,  and  unprogressive  people,  utterly  different  from  the  wideawake, 
progressive  race  which  alone  could  have  built  the  ruins.  Doubtless  they  had  much  of  the 
ancient  blood  in  them,  but  they  made  no  claim  to  any  knowledge  or  even  any  tradition  of 
the  construction  of  the  wonderful  structures  among  which  they  dwelt.  Even  in  so  vital  a 
matter  as  the  supply  of  water  they  had  fallen  utterly  below  the  state  of  their  predecessors. 
In  a  country  such  as  Yucatan,  the  water  supply  is  one  of  the  most  vital  problems.  The 
ancient  people  were  so  skillful  in  conserving  water  in  cisterns  and  other  artificial  reservoirs 
that  they  built  their  great  cities  without  reference  to  the  ‘‘cenotes”  or  caves,  the  only 
natural  source  of  permanent  supply.  At  the  time  of  the  Conquest,  however,  the  Spaniards 
found  practically  all  the  Mayas  clustered  about  the  “cenotes”  and  dependent  upon  them 
for  water.  They  had  utterly  degenerated  from  the  vigor  and  originality  of  their  ancestors, 
and  were  much  more  different  from  them  than  the  modern  Greeks  are  from  their  ancestors 
in  the  days  of  Plato  and  Phidias.  The  modern  Yucateco  does  not  begin  to  have  the 
energy  and  initiative  of  the  modern  Greek,  but  it  is  probably  no  exaggeration  to  say  that 
his  predecessors  were  the  equals  of  the  Greeks  or  any  other  race  so  far  as  real  achievement 
is  concerned.  I  know  that  this  is  a  sweeping  statement,  and  I  shall  return  to  it  later. 
Here  it  is  enough  to  point  out  that  the  Greeks  borrowed  much  of  their  culture  from  their 
neighbors ;  the  Mayas  had  no  one  from  whom  to  borrow.  The  Greeks  had  at  their  command 
the  accumulated  store  of  knowledge  and  of  tools  from  half  a  dozen  great  nations;  the 
Mayas  had  only  their  own  culture  and  their  own  crude  tools  to  rely  on.  Each  of  these 
two  nations  was  great  because  it  was  full  of  new  ideas.  We  know  the  ideas  of  the  Greeks 
not  only  from  their  ruins,  but  from  their  books.  Those  of  the  Mayas  are  known  only 
from  their  ruins,  and  yet  those  ruins  show  that  in  art,  architecture,  and  the  allied  crafts, 
brilliant  ideas  must  have  been  as  numerous  as  among  the  Greeks. 

The  genuine  greatness  of  the  ancient  Yucatecan  civilization  deserves  as  much  emphasis 
as  does  the  degeneration  of  their  successors.  The  measure  of  a  nation’s  greatness  is 
found  by  dividing  its  achievements  by  its  opportunities.  Let  us  attempt  to  sum  up  the 
achievements  of  the  ancient  Mayas.  In  the  first  place  they  developed  a  system  of  art 
and  architecture  which  need  not  shrink  from  comparison  with  that  of  Egypt,  Assyria, 
China,  or  any  other  nation  prior  to  the  rise  of  Greece.  Secondly,  they  appear  to  have 
developed  a  system  of  communications  much  easier  than  would  exist  to-day  except  for  the 
railroads.  Otherwise  they  could  not  possibly  have  maintained  so  high  a  state  of  civilization. 
Then,  again,  they  had  a  highly  advanced  system  of  water-supply.  In  the  days  before 
the  discovery  of  iron,  deep  wells  could  not  be  dug  and  primitive  people  could  live  nowhere 
except  close  to  the  deep  caverns  of  the  cenotes,  or  beside  the  temporary  '^aguadas”  or 
water-holes.  Yet  the  main  ruins  have  nothing  to  do  with  cenotes  or  natural  aguadas. 
They  are  often  miles  from  them  and  are  located  in  places  where  the  only  modern  water- 
supply  comes  from  wells  150  to  250  feet  deep.  Apparently  cisterns  were  constructed  on  a 


THE  PENINSULA  OF  YUCATAN. 


185 


large  scale,  as  may  be  inferred  from  a  few  which  still  remain  almost  intact.  Evidence  of 
another  kind  of  high  achievement  is  found  in  the  size  of  the  cities.  People  who  could 
live  in  such  vast  numbers  and  could  carry  on  such  great  public  works  must  have  had  a 
highly  organized  and  effective  social  and  political  system;  otherwise  chaos  would  have 
ensued.  And  finally  the  ancient  Yucatecos  are  thought  by  some  authorities  to  have  been 
on  the  point  of  taking  one  of  the  most  momentous  steps  in  human  progress.  They  had 
developed  a  system  of  hieroglyphics,  and  were  apparently  beginning  to  evolve  the  use  of  a 
definite  character  to  represent  a  definite  sound,  instead  of  a  character  for  each  separate 
word,  a  step  which  the  Chinese,  able  as  they  are,  have  never  taken. 

The  more  one  studies  the  problem,  the  more  one  feels  that  the  ancient  Yucatecos  were 
full  of  new  ideas;  and  in  the  last  analysis  ideas  are  the  cause  of  human  progress.  It  is 
possible,  to  be  sure,  that  the  seeds  of  some  ideas,  such  as  hieroglyphic  writing,  came  origi¬ 
nally  from  the  eastern  hemisphere — from  Egypt  perchance,  or  China,  or  some  other  part 
of  the  Old  World.  We  can  not  here  discuss  this  view,  although  it  seems  to  be  far  from 
proven.  This  much,  however,  will  be  admitted,  even  by  those  who  accept  it:  the  con¬ 
nection  between  the  Old  World  and  the  New,  if  any  ever  existed,  was  brief  and  one  might 
say  almost  accidental.  There  was  quite  surely  no  such  thing  as  any  prolonged  intercourse 
whereby  for  centuries  ideas  and  methods  of  thought  and  action  were  transferred  across 
the  water.  They  will  also  admit  that  the  wonderful  ruins  of  Yucatan  and  of  the  neighboring 
Maya  areas  are  distinctly  Mayan  in  style.  Whatever  may  have  been  imported  from 
other  parts  of  the  world  had  remained  long  in  Central  America  and  had  been  remodeled 
to  fit  the  genius  of  the  old  American  race  before  it  became  fixed  in  the  great  structures 
which  now  arouse  our  admiration.  Mayan  ideas  in  art,  Mayan  methods  of  supplying 
water  in  a  land  where  there  is  no  surface  water,  and  Mayan  peculiarities  of  religion  and 
taste  had  become  strongly  developed.  Therefore  we  must  conclude  that  even  if  some 
race  from  abroad  did  originally  bring  civilization  to  the  land,  a  matter  which  most  of  the 
best  authorities  deny,  the  newcomers  did  not  stagnate  and  deteriorate,  as  seems  to  be  the 
case  with  modern  immigrants  to  this  region  after  a  generation  or  two.  They  did  not 
imbibe  the  tropical  languor  which  ultimately  seems  to  check  progress  unless  there  is  a  con¬ 
tinual  stimulus  from  without.  They  kept  on  working,  and  developing  new  ideas  for 
generation  after  generation.  They  had  the  industry  to  make  some  of  the  world’s  finest 
ruins,  fashioned  of  carefully  hewn  stones  and  ornamented  with  wonderful  carvings;  and 
they  did  it  all  without  the  aid  of  iron,  and  with  no  apparent  stimulus  from  without.  At 
the  most  the  people  of  Maya  land  can  scarcely  have  borrowed  from  other  nations  a  tenth 
as  much  as  is  borrowed  by  all  modern  nations,  or  even  as  was  borrowed  by  the  Greeks. 
If  any  race  ever  worked  out  its  own  salvation,  it  was  the  ancient  Mayas.  To  develop  so 
far  must  have  required  many  centuries,  and  so  we  may  safely  say  that  the  Mayas  were 
once  continuously  blessed  with  an  activity  of  mind  and  body  comparable  to  that  of  almost 
any  part  of  the  world.  The  stimulus  to  such  activity  can  scarcely  have  come  from  other 
countries.  Was  it  something  in  the  fiber  of  the  original  race,  or  was  it  something  in  their 
environment? 

Before  we  attempt  to  discuss  this  question,  let  us  measure  the  achievements  of  the 
Mayas  by  still  another  standard.  Thus  far  we  have  confined  our  attention  to  the  ruins 
of  the  relatively  dry  bush-  or  jungle-covered  portion  of  Yucatan,  but  an  even  greater  num¬ 
ber  lie  to  the  south  and  southwest  as  far  as  Honduras  and  Chiapas.  Many  are  located 
in  the  densest  kind  of  forest.  The  description  of  the  one  rather  small  ruin  of  this  type 
which  I  was  able  to  visit  in  Yucatan  will  indicate  the  conditions  in  which  they  are  located. 
Lake  Kichankanab,  it  will  be  remembered,  lies  on  the  edge  of  the  tropical  forest,  equidistant 
from  the  Gulf  of  Mexico  on  the  west,  the  northern  shore  of  Yucatan  on  the  north,  and  the 
Caribbean  Sea  on  the  east,  100  miles  from  each  of  them.  The  difficulty  of  making  clearings 
and  the  virulence  of  malarial  fevers  cause  the  inhabitants  to  be  limited  to  a  few  widely 


186 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


scattered,  barbarous  Indians  and  a  temporary  population  of  “chicleros,”  or  men  who  come 
for  a  few  months  to  gather  the  sap  of  the  zapote  tree  for  the  purpose  of  converting  it  into 
chewing  gum.  The  chicleros  are  employed  on  a  great  concession,  which  covers  several 
thousand  square  miles,  but  whose  headquarters  at  Esmeralda  boast  of  nothing  more  than 
four  or  five  palm-thatched  sheds.  Starting  from  this  place,  we  rode  a  mile  along  a  trail  so 
narrow  and  blocked  with  vegetation  that  the  Mexican  guides  had  to  hew  down  almost 
innumerable  dead  limbs  and  lianas,  although  the  trail  had  been  in  use  only  the  preceding 
year.  At  the  top  of  a  small  ridge  overlooking  the  southern  end  of  Lake  Kichankanab  we 
came  upon  the  little  ruins  of  Elemax.  When  one  of  the  attendants  had  chopped  away  the 
vines  from  the  first  structure  it  proved  to  be  a  mass  of  stones  forming  a  mound  measuring 
about  65  feet  by  35.  Clearly  there  once  stood  here  a  solid  structure  in  the  usual  style  of 
ancient  Yucatan,  a  series  of  rooms  roofed  with  steep-sided,  flat-topped,  false  arches  ending 
in  capstones  instead  of  keystones.  The  surface  stones,  both  inside  and  out,  were  carefully 
smoothed  and  fitted,  and  those  on  the  corners  were  neatly  rounded.  Twenty  feet  away 
lay  a  similar  mound,  90  feet  by  55,  and  others  were  located  all  around.  Our  guide 
conducted  us  to  the  end  of  this  particular  group  of  ruins.  We  followed  a  winding  forest 
trail  made  by  chicleros  on  their  way  to  find  zapote  trees  which  they  could  tap  for  gum. 
The  trail,  of  course,  was  made  without  the  slightest  reference  to  ruins;  moreover,  the 
undergrowth  of  the  forest  is  so  dense  that  the  largest  sort  of  mound  100  feet  away  would 
be  as  invisible  as  though  on  the  other  side  of  the  world;  and  small  mounds  are  hidden  at  a 
distance  of  20  or  30  feet.  Nevertheless,  in  the  space  of  scarcely  a  mile  we  saw  at  least 
20  mounds.  Manifestly,  if  the  vegetation  were  cleared  away  many  more  would  be  in  sight. 
The  guide  stated  that  in  his  hunting  trips  he  comes  across  similar  mounds  very  frequently, 
“everywhere,”  as  he  put  it.  Among  those  that  we  saw  the  great  majority  were  small 
structures,  probably  houses,  but  a  few  of  larger  size  appear  to  have  been  temples.  Near 
the  temples  stand  two  structures,  now  only  about  15  feet  high,  which  seem  to  have  been 
pyramids  designed  for  sacrificial  purposes  or  for  some  other  religious  rites.  The  whole 
aspect  of  the  ruins  is  like  that  of  those  in  the  jungle  region  farther  north,  save  that  here 
in  the  forest  the  degree  of  destruction  is  greater  and  the  original  magnificence  less.  It  is 
possible  that  all  of  the  houses  were  not  occupied  at  once,  but  even  if  this  is  so,  the  ruins 
clearly  represent  a  considerable  population  of  permanently  settled  agricultural  people  who 
went  to  the  trouble  of  hewing  stone  for  their  temples  and  other  public  structures.  They 
must  have  cleared  the  forest  and  raised  crops  in  the  clearings  permanently. 

Similar  and  far  more  striking  phenomena  in  other  parts  of  the  Maya  country  point  to 
an  even  denser  population  in  the  deep  forests.  For  instance,  Palenque,  in  the  Mexican 
state  of  Chiapas,  southwest  of  Yucatan,  and  Tikal,  farther  to  the  east,  are  famous  as  the 
sites  of  some  of  the  most  magnificent  ruins  in  America,  ruins  which  not  only  are  massive, 
but  are  beautifully  and  elaborately  carved.  They  are  located  in  what  is  described  as  the 
densest  kind  of  tropical  forest.  The  size  of  the  ruins  and  their  large  amount  of  sculpture 
indicate  that  the  surrounding  cities  must  have  been  long  inhabited  by  a  dense  population. 
Moreover,  the  people  must  have  been  highly  industrious  or  they  never  could  have  accom¬ 
plished  such  great  results,  especially  when  they  had  no  iron  tools  to  aid  them — nothing  but 
stone,  so  far  as  has  yet  been  determined. 

All  this  may  perhaps  seem  alien  to  our  main  subject  of  changes  of  climate,  but  it  is  by 
no  means  so,  for  it  raises  a  great  question.  To-day,  as  we  have  seen,  the  dampness  of 
the  forest,  its  equable  temperature,  its  fevers,  and  its  over-exuberant  vegetation  prevent 
its  conquest  not  only  by  the  primitive  Indians,  but  by  the  Mexicans  or  the  Spaniards. 
Nowhere,  under  similar  conditions,  has  any  modern  race  succeeded  in  really  overcoming 
the  tropical  forest  as  distinguished  from  the  tropical  jungle.  Yet  long  ago  the  ancient 
Mayas  must  have  cleared  and  cultivated  great  areas  of  what  is  now  dense  forest  beyond 
the  power  of  modern  man. 


THE  PENINSULA  OF  YUCATAN. 


187 


Let  us  turn  back  now  to  the  other  factor  in  the  equation  of  a  nation’s  greatness,  the 
opportunities  which  serve  as  the  divisor  of  the  achievements.  Of  the  outward  helps  which 
we  modern  nations  deem  necessary  to  great  accomplishment  the  Mayas  had  practically 
none.  They  possessed,  to  be  sure,  a  country  capable  of  raising  abundant  crops  and  sup¬ 
porting  a  large  population.  Of  other  natural  advantages,  at  least  of  those  commonly 
recognized  as  such,  they  had  practically  none.  We  have  already  emphasized  the  fact  that 
Yucatan  is  so  isolated  that  without  modern  means  of  communication  she  would  even  now 
have  no  neighbors  from  whom  she  could  gather  suggestions  or  who  would  stimulate  her 
by  example  or  immigration.  If  we  consider  the  entire  Maya  country,  the  same  is  true. 
The  only  neighboring  region  which  could  possibly  have  stimulated  her  is  Mexico,  but  the 
Zapotecan,  Nahua,  and  other  civilizations  of  that  country  by  no  means  rivaled  that  of 
Maya  land,  and  most  of  them  appear  to  have  been  her  imitators  rather  than  her  examples. 

Two  other  matters  are  even  more  important  than  the  lack  of  any  people  from  contact 
with  whom  the  Mayas  might  have  profited.  These  are  the  complete  absence  of  beasts  of 
burden  and  of  iron  tools  in  pre-Columbian  days.  In  previous  pages  we  have  seen  the 
almost  immeasurable  disadvantage  of  the  nation  which  lacks  these  two  fundamental  aids 
to  progress.  The  Mayas  must  have  toiled  incessantly  in  carrying  on  their  backs  the 
stones,  mortar,  and  beams  of  their  buildings.  Yet  this  did  not  check  their  work.  They  had 
no  hesitation  in  transporting  stones  8  or  10  feet  long,  although  this  must  have  required 
laborers  by  the  score.  Moreover,  all  the  food  of  the  people,  not  merely  that  of  the  farmers 
but  that  of  the  city  people  and  of  the  thousands  of  workmen  engaged  in  building  the  ruins, 
had  to  be  brought  from  the  fields  on  the  backs  of  human  animals,  a  task  which  only  a 
nation  full  of  energy  and  resolution  would  or  could  accomplish.  The  absence  of  beasts  of 
burden,  however,  was  a  small  matter  compared  with  the  absence  of  iron.  We  are  told 
sometimes  that  the  ancient  Americans  had  tools  of  hardened  copper,  but  this  is  pure 
theory.  We  have  never  found  an  ounce  of  such  copper  and  we  do  not  know  how  it  could 
be  made.  The  sole  reason  for  assuming  its  existence  is  that  we  do  not  see  how  the  ancient 
people  could  have  done  such  clever  work  without  some  such  material.  We  fail,  however, 
to  appreciate  the  fact  that  tools  of  obsidian  or  flint  can  be  made  of  great  delicacy  by  a 
people  who  have  sufficient  skill,  energy,  and  patience.  In  these  last  words  we  come  once 
more  to  the  crux  of  the  whole  matter.  The  Mayas  possessed  such  a  degree  of  mental 
and  physical  energy  that,  in  spite  of  obvious  disadvantages,  they  took  the  crude  tools  at 
their  command  and  were  able  to  arrive  at  a  stage  of  civilization  which  was  possibly  higher 
than  that  attained  by  any  other  race  with  no  larger  opportunities.  Their  achievements, 
when  measured  absolutely,  fall  far  behind  those  of  Greece,  and  still  more,  perhaps,  behind 
those  of  the  modern  nations  of  Europe  and  America,  but  when  measured  according  to  their 
opportunities,  their  achievements  seem  to  be  worthy  of  comparison  with  those  of  almost 
any  race. 

Leaving  aside  the  many  mooted  questions  concerning  the  ancient  Mayas,  let  us  sum 
up  one  or  two  points  which  stand  out  with  especial  clearness.  In  the  first  place,  the  natives 
of  Yucatan,  which  is  at  present  the  most  favored  part  of  Maya  land,  are  to-day  slow  and 
inert,  not  given  to  exertion  of  any  kind,  and  not  in  the  least  inclined  to  develop  new  ideas 
and  bring  them  to  fruition  by  arduous  labor.  In  the  second  place,  European  immigrants 
quickly  acquire  the  inefficient  habits  of  the  natives,  and  in  two  or  three  generations  appear 
to  cease  to  be  energetic  enough  to  carry  out  new  ideas  although  they  may  perhaps  have 
them.  In  the  third  place,  the  conquest  of  the  tropical  forests  is  a  task  beyond  the  power 
of  any  of  the  modern  tropical  races,  even  though  they  have  good  steel  tools  to  help  them. 
Moreover,  it  is  doubtful  whether  any  European  race  could  as  yet  conquer  the  forest  and 
raise  crops  in  it  in  the  face  of  the  enervating  climate  and  the  debilitating  fevers.  In  the 
past,  however,  the  exact  contrary  was  true  in  respect  to  all  three  of  these  points.  The 
natives  of  Yucatan  were  not  slow  and  inert,  but  were  highly  inventive  and  energetic. 


188 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Immigrants  from  other  regions,  if  such  were  really  the  bringers  of  the  seeds  of  civilization, 
did  not  degenerate  rapidly,  for  their  descendants  must  have  been  full  of  energy  and  initiative 
for  centuries  before  a  culture  so  highly  impregnated  with  local  character  could  have  devel¬ 
oped.  And  finally  the  ancient  people  succeeded  in  conquering  regions  that  now  are 
unconquerably  forested  and  feverish. 

In  order  to  explain  this  strange  contradiction  between  the  past  and  the  present  two 
possibiUties  present  themselves.  The  first  is  that  the  ancient  inhabitants  of  Yucatan,  in 
spite  of  their  lack  of  beasts  of  burden  and  tools  of  iron,  could  accomplish  all  manner  of 
things  which  modern  man  can  not.  They  could  clear  and  cultivate  the  dense  forest,  they 
could  resist  its  debilitating  fevers,  they  could  work  with  constant  energy  in  spite  of  the 
enervating  climate,  and  they  could  persist  in  doing  all  these  things  for  centuries.  In 
other  words,  they  were  greatly  superior  to  any  modern  race.  This  is  the  common,  although 
unexpressed  assumption.  The  other  possibility  is  that  the  rainfall  was  formerly  less  than 
at  present,  so  that  regions  now  covered  with  forest  then  bore  only  jungle,  that  fevers  were 
less  abundant  than  now,  and  that  the  climate  was  not  so  enervating.  This  second  possi- 
bilit3^  seems  to  demand  less  radical  assumptions  than  the  first.  It  simply  requires  us  to 
believe  that  the  same  sort  of  thing  has  happened  in  Yucatan  which  we  have  reason  to 
believe  has  happened  elsewhere. 


y  ■*:  ■  ■  ■  '•^f’' '  ‘  ^  ■  ' -v;  ,  '' 

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'-  ',^  *  ->'i  '  -'mm  .  ^ 


HUNTINGTON 


PLATE  9 


c 


A.  Carved  head  at  Baul  in  the  Pacific  coffee  belt  of  western  Guatemala. 

B.  Fragment  of  a  temple  wall  at  Copan. 

C.  One  of  the  Stelae  at  Copan. 

D.  Forest  in  which  the  ruins  at  Kichen-kanab  are  located. 


CHAPTER  XVI. 


THE  SHIFTING  OF  CLIMATIC  ZONES. 

In  the  preceding  chapters  we  have  seen  that  in  few  parts  of  the  world  is  there  a  greater 
contrast  between  the  past  and  the  present  than  in  Yucatan  and  the  surrounding  regions 
of  Maya  culture.  This  is  preeminently  the  case  in  those  districts  where  magnificent  ruins 
are  located  in  the  midst  of  dense  and  uninhabitable  forests.  We  have  seen  further  that 
the  ancient  Mayas  were  undoubtedly  a  remarkably  efficient  people,  in  striking  contrast  to 
the  notable  inefficiency  of  the  present  inhabitants  of  the  torrid  zone  and  especially  of  the 
inhabitants  of  densely  forested  areas.  Furthermore,  according  to  the  overwhelming 
evidence  of  the  ruins  the  Mayan  cultiu'e  developed  where  we  now  find  its  traces,  and  this 
development  must  have  demanded  many  centuries  of  growth  previous  to  the  many  centuries 
during  which  it  bore  fruition  in  the  great  temples  and  cities  whose  remnants  we  now 
admire.  These  facts  lead  to  the  further  conclusion  that  if  the  physical  conditions  of 
Maya  land  were  the  same  in  the  past  as  in  the  present,  the  ancient  Mayas,  in  sharp  dis¬ 
tinction  from  their  descendants,  must  have  possessed  a  degree  of  energy  and  a  power  of 
resistance  to  the  debihtating  effects  of  a  tropical  climate  far  in  excess  of  that  of  any  other 
race  now  existing.  This  is  certainly  a  possibihty  and  can  not  be  lightly  dismissed.  It  is 
one  of  those  possibihties  which  can  not  be  proved  and  which  are  often  adopted  as  a  refuge 
when  all  other  theories  fail.  Other  possibilities,  such  as  the  introduction  of  culture  from 
the  eastern  hemisphere  or  the  invasion  of  Maya  land  by  some  alien  race  possessed  of  an 
uncommonly  high  culture,  are  more  and  more  being  universally  negatived  by  the  work  of 
recent  scholars.  Still  another,  and  (so  far  as  now  appears)  perhaps  the  only  other  genuine 
possibihty  is  that  in  the  past  the  climate  was  so  much  drier  than  now  that  the  present 
forested  areas  were  covered  merely  with  jungle  instead  of  with  large  trees.  Such  an  assump¬ 
tion  at  first  sight  appears  to  be  directly  opposed  to  om  general  conclusion  that  the  south¬ 
western  United  States  and  central  Asia  are  now  on  the  whole  distinctly  drier  than  in  the 
past,  but  such  is  by  no  means  the  case.  Let  us  first  see  how  much  ground  there  is  for 
beheving  that  climatic  changes  of  any  sort  have  occurred  in  Yucatan.  Then  let  us  investi¬ 
gate  the  probable  nature  and  effects  of  any  such  possible  changes;  and  finally  let  us  test 
all  our  conclusions  by  the  rigorous  method  of  a  comparison  of  the  dates  indicated  by  our 
California  curve  and  the  dates  of  Maya  history  so  far  as  they  have  been  ascertained. 

Writers  on  Yucatan  have  sometimes  suggested  that  the  country  could  not  formerly 
have  supported  so  vast  a  population  had  not  the  rainfall  and  the  agricultural  possibilities 
been  greater  than  at  present.  Others  deny  this.  They  say  that  an  industrious  and  active 
people  who  had  the  energy  and  brain-power  to  construct  wells  and  reservoirs  could  culti¬ 
vate  almost  every  foot  of  Yucatan  proper  except  for  the  numerous  spots  where  the  bare 
rock  actually  comes  to  the  surface.  One  can  ride  for  days  over  plains  of  rich  soil,  deep,  soft, 
and  easy  to  cultivate,  but  abandoned  to  the  jungle  and  to  wild  beasts.  The  reason  is  the 
difficulty  of  digging  wells  or  building  reservoirs,  or  else  the  prevalence  of  fevers.  Except 
for  an  insignificant  coastal  strip  where  no  ruins  are  found,  Merida  is  as  dry  as  any  portion 
of  Yucatan;  yet  the  five  months  of  the  rainy  season  from  June  to  October  have  26.5  inches 
of  rain,  which  is  decidedly  more  than  the  eastern  United  States  gets  during  the  same  period 
and  is  sufficient  to  allow  good  crops  of  corn  to  be  raised  almost  everywhere.  That  lack  of 
rainfall  has  nothing  to  do  with  the  present  comparative  depopulation  of  Yucatan  is  evident 
enough  from  the  fact  that  the  densest  and  most  progressive  population  is  found  in  the 

189 


190 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


driest  part  of  the  peninsula.  In  fact,  as  has  been  pointed  out  in  our  discussion  of  the 
jungle  and  the  forest,  a  small  rainfall  is  a  distinct  advantage,  because  it  prevents  the  growth 
of  the  great  tropical  forest  which  so  effectively  checks  human  progress.  If  the  rainfall 
of  the  past  had  been  greater  than  that  of  the  present,  the  effect  would  have  been  to  diminish 
rather  than  increase  the  density  of  population. 

There  appears,  then,  to  be  no  reason  for  thinking  that  Yucatan  has  suffered  a  diminution 
of  rainfall  similar  to  that  of  Arizona  or  of  the  portions  of  Asia  in  temperate  latitudes. 
Nevertheless,  the  lakes  and  terraces  of  the  Valley  of  Mexico  and  the  great  terraces  of  the 
state  of  Oaxaca  furnish  strong  evidence  that  a  marked  change  of  some  sort  has  taken  place 
in  those  regions;  and  if  such  has  been  the  case  there,  Yucatan,  which  hes  but  500  miles  from 
Oaxaca  and  from  1  to  4  degrees  farther  north,  can  scarcely  have  failed  to  be  affected. 
At  these  southern  points,  however,  the  effect  need  not  necessarily  have  been  of  the  same 
type  as  that  produced  farther  north — in  New  Mexico,  for  example — since  the  two  places 
lie  in  different  climatic  zones. 

The  general  effect  of  changes  of  climate  seems  to  be  to  shift  the  peculiarities  of  one  lati¬ 
tude  into  another  or,  perhaps  more  accurately,  to  cause  the  seasonal  shifting  of  zones  to 
vary  in  amount  and  intensity.  Inasmuch  as  the  chief  change  during  the  past  2,000  to 
3,000  years  in  the  regions  30°  to  40°  north  of  the  equator  appears  to  have  been  in  the 
direction  of  aridity,  the  general  shifting  seems  to  have  carried  the  conditions  of  more 
southerly  regions  into  those  farther  north.  This  would  seem  to  mean  that  at  the  beginning 
of  the  Christian  era  or  earlier  the  zone  of  westerly  storms,  during  the  winter,  but  not 
necessarily  in  summer,  lay  farther  south  than  to-day,  and  thereby  made  the  present 
subtropical  zone  less  arid  than  at  present.  The  natural  corollary  of  this  would  be  that 
the  subtropical  zone  of  aridity  was  also  displaced  southward.  This  would  have  led  to  a 
diminution  of  winter  rainfall  and  hence  of  vegetation  along  the  northern  edge  of  the  equa¬ 
torial  zone  in  those  parts  where  inblowing  trade  winds  combine  with  equatorial  low  pressure 
to  produce  abundant  rain  at  all  seasons.  Thus  jungle  would  have  been  caused  to  take  the 
place  of  genuine,  dense  forests  in  those  particular  regions,  and  jungle  might  in  turn  be 
replaced  by  bush.  In  Yucatan  and  other  parts  of  the  extreme  south  of  Mexico,  or  in 
Central  America,  the  transition  from  jungle  to  forest  is  often  quite  sudden.  For  instance, 
in  Yucatan  it  occurs  within  a  distance  of  30  to  40  miles.  If  the  line  of  transition  were 
shoved  southward  200  to  300  miles,  it  would  cause  jungle  to  prevail  in  practically  all  the 
places  where  ruins  are  now  found. 

Such  a  change  as  has  just  been  described  would  not  merely  explain  the  location  of 
great  ruins  in  regions  now  too  densely  forested  to  be  habitable;  it  would  also  to  a  certain 
extent  relieve  us  of  the  necessity  of  assuming  that  the  ancient  Yucatecos  possessed  a  degree 
of  energy  and  ability  out  of  harmony  with  anything  which  now  exists  in  regions  so  warm 
and  debilitating  as  Yucatan. 

Before  explaining  this,  however,  it  will  be  well  to  examine  more  closely  the  probable 
mechanism  of  a  shifting  of  the  great  climatic  zones.  This  can  best  be  understood  by 
considering  first  what  happens  during  our  ordinary  winters.  Most  of  the  rainfall  of  the 
United  States,  as  everyone  knows,  is  derived  from  cyclonic  storms — that  is,  from  great 
areas  of  low  pressure  and  inblowing  winds  which  may  have  a  diameter  of  1,000  or  more  miles, 
and  which  sweep  across  the  country  with  a  general  easterly  trend  in  obedience  to  the 
prevailing  direction  of  the  winds  in  temperate  latitudes.  The  courses  of  these  storms,  so 
far  as  they  are  understood,  are  determined  by  the  differences  in  pressure  between  the 
several  more  or  less  permanent  areas  of  high  or  low  barometer  which  center  over  oceans  and 
lands  in  various  latitudes  and  with  varying  degrees  of  intensity  at  different  seasons.  In 
general,  storms  move  out  from  or  around  areas  of  high  pressure  and  are  drawn  toward  those 
of  low  pressure.  Anything  which  changes  the  location  or  intensity  of  the  major  pressure 
areas  changes  the  course  and  intensity  of  storms.  The  North  Atlantic  Ocean,  by  reason 


THE  SHIFTING  OF  CLIMATIC  ZONES. 


191 


of  the  high  degree  to  which  it  is  warmed  by  the  Gulf  Stream,  is  a  most  important  area  of 
permanent  low  pressure.  To  this  is  thought  to  be  due  in  large  measure  the  fact  that  the 
northern  United  States  and  Canada  on  the  west  and  northwestern  Europe  on  the  east, 
together  with  the  Atlantic  Ocean  between  them,  are  the  most  stormy  regions  of  the  globe. 
In  summer,  when  the  continents  become  warm  and  therefore  are  characterized  by  low 
pressure,  the  North  Atlantic  low  area  loses  its  importance.  The  difference  in  pressure 
between  land  and  sea  is  slight,  and  the  storms  are  correspondingly  mild.  They  move 
nearly  from  west  to  east,  although  of  course  with  many  curves,  and  their  tracks  are  usually 
located  well  up  toward  the  north.  In  winter,  on  the  contrary,  the  continents  cool  off  and 
become  areas  of  pronounced  high  pressure,  while  the  oceans  are  areas  of  low  pressm*e. 
At  this  time  the  difference  in  pressure  between  North  America  and  the  North  Atlantic 
reaches  a  maximum,  the  barometric  gradients  are  steep,  and  storms  are  correspondingly 
fierce.  The  courses  of  the  storms  under  such  conditions  are  more  curved  than  in  summer 
and  lie  farther  south.  The  center  of  the  continent  becomes  so  cold  that  an  extensive 
area  of  permanent  high  pressure  is  formed;  from  this  the  winds  blow  outward.  Thus  the 
storms  which  would  otherwise  move  more  or  less  directly  east  from  the  Pacific  to  the 
Atlantic  are  pushed  in  many  cases  far  to  the  south.  Starting  in  California,  a  storm  may 
swing  southeast  into  Arizona  and  Texas,  and  then  move  east  and  finally  come  up  the 
Atlantic  coast  and  swing  off  toward  the  low  center  of  the  North  Atlantic.  In  its  wake  such 
a  storm  may  send  the  thermometer  down  to  20°  F.  in  southern  Arizona  and  kill  the  peach 
blossoms  which  have  opened  too  early;  then  it  may  go  on  to  produce  a  “norther”  with  a 
temperature  of  50°  in  Yucatan,  and  to  kill  the  orange  trees  in  Florida.  The  number  of 
storms  which  follow  such  southerly  courses  varies  greatly  from  year  to  year.  Upon  these 
variations  the  character  of  the  winter  largely  depends.  In  1911-12,  for  example,  the 
northern  parts  of  the  United  States  had  few  storms  and  slight  snowfall  as  a  general  rule 


Fig.  51. — Storm  Frequency,  1878-1887.  (After  Dunvvoody.) 


192 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


during  the  middle  of  the  winter,  although  this  was  compensated  for  toward  spring.  Farther 
south,  however,  storms  which  had  gone  far  equatorward  brought  to  Texas  and  northern 
Mexico  more  than  the  usual  amount  of  rain,  while  Yucatan  also  had  a  comparative  abun¬ 
dance  of  showers  and  of  “northers.”  The  conditions  were  by  no  means  remarkable,  but 
they  serve  to  illustrate  the  fact  that  variations  in  the  tracks  of  the  storm  bring  with  them 
important  results  in  the  way  of  variations  in  rainfall  and  temperature.  The  winter  of 
1911-12  was  characterized  by  a  relatively  pronounced  and  long-continuing  area  of  high 
pressure  over  the  central  part  of  North  America,  and  therefore  the  storms  for  a  season  went 
far  to  the  south.  In  1912-13  exactly  the  reverse  took  place.  The  continental  high-pressure 
area  was  poorly  developed,  the  storms  moved  over  northerly  tracks,  and  the  northern 
United  States  was  uncommonly  warm. 

Having  seen  that  the  general  course  of  the  storm  tracks  varies  from  year  to  year,  our 
next  question  is  whether,  if  longer  periods  than  a  year  are  considered,  the  average  track 
shows  any  variation.  Dunwoody  some  years  ago  began  the  investigation  of  this  matter, 
and,  so  far  as  data  were  available,  made  a  map,  figure  51,  showing  the  average  number 
of  storm  centers  passing  over  each  5  degrees  square  of  the  northern  hemisphere.  His  map 
shows  that  the  number  of  storms  is  greatest  in  the  region  of  the  Great  Lakes  of  North 
America,  and  is  large  throughout  all  of  the  northern  United  States,  southern  Canada, 
northwestern  Europe,  and  Japan.  Professor  C.  J.  Kullmer,  of  the  University  of  Syracuse, 
has  made  a  study  of  this  map  and  has  pointed  out  that  it  affords  some  most  interesting 
suggestions  as  to  the  possible  relation  between  high  civilization  and  climatic  instability. 
In  a  later  publication  I  shall  consider  this  matter  at  length,  but  for  our  present  purpose  the 
important  matter  is  that  his  work  enables  us  to  compare  the  storm  tracks  at  two  periods 
separated  by  an  interval  of  12  years.  Inasmuch  as  his  original  data  have  never  been 
published,  and  as  they  are  important  not  only  for  our  present  purpose,  but  for  other 
climatological  studies,  I  have  persuaded  him  to  prepare  the  contribution  which  follows. 


THE  SHIFT  OF  THE  STORM  TRACK. 


By  Charles  J.  Kullmer. 


Our  only  maps  of  the  storm  frequency  of  the  whole  of  the  northern  hemisphere  (we 
have  none  of  the  southern  hemisphere)  are  those  of  H.  H.  Dunwoody,  published  in  1893, 
and  covering  the  10-year  period  from  1878  to  1887.  The  storm  frequency  is  given  in 
separate  maps  for  each  month,  and  these  are  combined  into  a  year  map.  Dunwoody 
divides  the  map  of  the  northern  hemisphere  into  squares  measuring  5°  on  a  side  and  records 
in  each  square  the  number  of  barometric  depressions  whose  centers  crossed  it  during  the 
period  under  discussion.  For  instance,  the  centers  of  306  depressions  passed  through  the 
Lake  Michigan  square,  or  about  30  barometric  depressions  a  year.  Practically  the  storm 
frequency  was  much  greater  than  this,  since  419  storms  passed  through  the  Lake  Superior 
square  on  the  north  and  177  storms  in  the  square  just  south;  but  this  ueed  not  concern  us, 
for  we  have  here  to  do  only  with  the  tracks  of  the  centers  of  depressions.  In  view  of  the 
importance  of  storms  in  many  phases  of  life,  it  has  seemed  worth  while  to  reconstruct 
the  storm  frequency  maps  for  the  United  States  for  the  latest  available  decade,  1899-1908, 
in  order  to  determine  whether  in  the  interval  of  21  years  any  general  shift  of  the  storm  track 
has  taken  place.  The  material  for  this  is  available  in  the  plotted  tracks  of  barometric 
depressions  given  in  the  monthly  summaries  of  the  “Monthly  Weather  Review.” 

Dunwoody  does  not  give  the  individual  tracks,  nor  does  he  describe  in  detail  the  methods 
used  in  constructing  his  charts,  so  that  there  is  some  doubt  as  to  the  extent  to  which  his 
material  may  be  considered  identical  with  that  used  in  the  present  investigation.  A  com¬ 
parison  of  the  maps  and  a  discussion  of  the  results,  however,  seems  to  show  that  the  material 
is  in  general  the  same  and  that  reliable  comparisons  are  possible. 

The  monthly  maps  of  the  United  States  for  the  new  series  of  observations  as  compared 
with  the  old  are  given  in  figures  52  to  63.  In  these  the  figures  represent  the  number  of  storm 
centers  for  each  5°  square,  those  of  Dunwoody  for  1878-1887  being  placed  above,  and  those 
of  the  later  period,  1899-1908,  below.  The  curved  lines  represent  the  number  of  storm 
centers  passing  through  a  given  square  each  year,  the  earlier  conditions  being  indicated  by 
dotted  lines  and  the  later  by  solid  lines.  In  the  first  map,  that  for  January,  figure  52, 
we  at  once  find  five  important  phenomena,  which  occur  also  on  later  maps  and  on  the 
year  map;  first,  an  increase  in  storm  frequency  over  the  southwestern  States;  second,  a 
decrease  in  the  west  in  latitude  40°  to  45°;  third,  a  great  increase  in  western  Canada;  fourth, 
a  general  southerly  movement  of  the  lines  of  equal  storm  frequency;  and  fifth  (and  perhaps 
most  interesting),  the  phenomenon  of  a  double  maximum  in  latitude  45°  to  50°  as  com¬ 
pared  with  the  single  maximum  of  the  earlier  period.  The  great  increase  in  western 
Canada  is  of  such  an  amount  as  to  suggest  a  difference  in  the  observational  material,  but 
this  is  not  necessarily  the  case,  as  will  appear  later. 

The  February  map,  figure  53,  shows  all  the  phenomena  of  that  for  January.  The 
southwestern  increase  in  storm  frequency  is  especially  marked,  the  number  of  centers 
passing  through  a  single  square  having  in  one  case  increased  from  9  to  32.  Just  to  the 
northeast  of  this  square  the  western  decrease  in  latitude  40°  to  45°  is  also  quite  pronounced. 
The  increase  in  western  Canada  and  the  southerly  shift  of  the  lines  as  a  whole  are  nearly 
as  marked  as  in  the  January  map,  while  the  double  maximum  is  less  distinct,  although  it 
clearly  exists.  March  (figure  54)  shows  most  prominently  the  southwestern  increase, 
while  the  general  southerly  shift  is  visible,  and  the  double  maximum  still  appears,  although 

14  193 


194 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA, 


Fig.  52. — Storm  Frequency.  January. 


Fig.  53. — Storm  Frequency.  February. 


THE  SHIFTING  OF  CLIMATIC  ZONES, 


195 


Fig.  55. — Storm  Frequency.  April, 


196 


E  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA 


Fig,  56. — Storm  Frequency.  May. 


Fig.  57. — Storm  Frequency  .  June. 


THE  SHIFTING  OF  CLIMATIC  ZONES 


197 


Fig.  58. — Storm  Frequency.  July. 


Fig.  59. — Storm  Frequency.  August. 


198 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Fig.  60. — Storm  Frequency.  September. 


Fig.  61. — Storm  Frequency.  October, 


THE  SHIFTING  OF  CLIMATIC  ZONES 


199 


Fig.  62.— Storm  Frequency.  November. 


Fig.  63. — Storm  Frequency.  December, 


200 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


its  eastern  member  has  moved  one  square  west  of  its  position  in  February.  The  western 
decrease,  however,  and  the  Canadian  increase  have  both  disappeared  almost  entirely. 
This  speaks  strongly  against  the  idea  that  the  differences  between  the  old  and  new  series 
of  maps  are  due  to  differences  in  the  observational  material  on  which  they  are  based. 
If  such  were  the  case  it  would  scarcely  be  possible  that  in  one  particular  month  there  shou  d 
be  a  sudden  reversal  of  previous  conditions,  so  that  the  number  of  observations  should 
suddenly  show  a  relative  increase  in  the  western  United  States  in  latitude  40°  to  45°  and  a 
large  decrease  in  Canada  10°  farther  north.  The  April  map  for  both  periods  (figure  55) 
shows  a  southwestern  maximum;  in  the  later  period,  however,  the  center  lies  farther  south 
and  west  than  in  the  earlier.  In  this  map  we  again  note  the  decrease  north  of  the  south¬ 
western  increase,  and  the  western  Canada  increase.  Each  period  shows  only  a  single 
eastern  maximum,  that  of  the  later  map  lying  well  to  the  west  of  the  other. 

May  (figure  57)  shows  the  southwestern  increase  and  a  slight  decrease  in  the  Oregon- 
Idaho  section.  Here  again  we  notice  only  a  slight  increase  in  western  Canada,  which 
gives  strength  to  the  reality  of  the  large  increases  shown  in  other  months.  Also  the  double 
maximum  has  almost  disappeared,  although  traces  of  the  western  center  may  be  seen  in 
the  27  tracks  which  crossed  the  square  between  45°  and  50°  N.  and  100°  and  105°  W.  In 
this  case  the  earlier  map  also  showed  a  double  maximum  indicated  by  the  figures  28  in 
the  square  between  90°  and  95°  W.  and  34  between  75°  and  80°  W.  June  (figure  57) 
shows  marked  western  Canadian  increase,  a  moderate  southwestern  increase,  a  double 
maximum,  a  slight  western  increase,  and  a  distinct  southward  shifting.  July  (figure  58) 
shows  strong  western  Canadian  increase,  double  maximum  and  southwestern  increase. 
August  (figure  59)  shows  western  Canadian  increase  and  a  westward  shift  of  the  maximum 
in  latitude  45°  to  50°.  September  (figure  60)  shows  general  westward  shift,  double  maxi¬ 
mum,  and  western  Canadian  increase.  October  (figure  61)  shows  the  southwestern 
increase,  the  decrease  just  north  of  it,  a  pronounced  increase  over  western  Canada,  and  a 
double  maximum  including  within  it  a  double  maximum  of  the  earlier  period.  The  agree¬ 
ment  of  the  peculiar  loop  in  the  southeastern  part  of  the  1  line  in  both  maps  is  striking. 
November  (figure  62)  presents  the  highest  increase  over  western  Canada,  a  double  maxi¬ 
mum  as  compared  with  the  single  maximum  of  the  earlier  period.  The  same  holds  also  for 
December  (figure  63).  The  Oregon-Idaho  decrease  is  here  marked.  There  is  also  a 
general  southerly  shift. 

Combining  these  month  maps  we  have  a  year  map  (figure  64),  showing  general  agree¬ 
ment  with  that  of  21  years  before,  but  characterized  by  the  phenomena  already  noticed 
in  the  month  maps — a  marked  increase  over  western  Canada,  a  slight  decrease  in  the  two 
western  squares  of  latitude  40°  to  45°,  and  a  general  southerly  and  westerly  shift  of  the 
lines  of  equal  storm  frequency.  In  latitude  45°  to  50°,  along  the  storm  track  proper,  a  single 
maximum  of  484  in  the  earlier  period  is  replaced  by  a  double  maximum,  480  and  491,  in 
the  later  period.  If  we  take  the  central  area,  which  may  be  supposed  to  have  had  400 
storms  in  each  case,  its  center  would  seem  to  fall  about  2.5°  farther  west  in  the  later  map 
than  in  the  earlier.  Little  reliance,  however,  can  be  laid  on  this.  Corresponding  to  the 
general  westerly  shift,  an  eastern  decrease  is  noted,  but  I  lay  less  weight  on  this  feature, 
since  I  am  convinced  that  the  tracks  as  given  in  the  monthly  summaries  are  not  continued 
over  the  ocean  in  all  cases  as  far  as  might  be  the  fact. 

Turning  now  to  the  discussion  of  the  meaning  of  the  maps,  let  us  consider  first  the 
phenomenon  of  a  double  maximum.  If  the  average  track  of  all  storms  be  plotted  it  forms 
a  curve  corresponding  to  the  line  of  greatest  frequency.  If  such  a  curved  line  merely 
touches  a  given  parallel  of  latitude,  say  that  of  47°  N.,  there  will  be  a  single  maximum  of 
storm  frequency  along  that  line.  If,  however,  the  curved  storm  track  is  shifted  enough 
so  that  its  most  southerly  point  lies  a  few  degrees  south  of  latitude  47°,  say  in  latitude  45°, 
the  storm  track  itself  will  cut  the  given  parallel  in  two  places.  Thus  along  that  latitude 


THE  SHIFTING  OF  CLIMATIC  ZONES. 


201 


we  should  get  a  double  maximum  where  previously  only  a  single  maximum  was  found. 
In  the  present  case  the  ideal  storm  track — that  is,  the  mean  of  all  tracks — may  be  con¬ 
sidered  as  running  in  a  great  arc  somewhat  southeasterly  from  a  point  in  western  Canada, 
approximately  in  latitude  55°  N.  and  longitude  115°  W.,  to  the  northern  part  of  Lake 
Superior,  eastward  across  southern  Canada,  and  then  with  a  slight  northerly  trend  toward 
Newfoundland.  The  area  of  greatest  storm  frequency  is  limited  to  a  small  region,  approxi¬ 
mately  45°  to  50°  north  of  the  equator.  Southward  the  number  of  storms  decreases  gradu- 


Fig.  64.— Storm  Frequency.  Year  Maps  for  1878-1887,  after  Dunwoody,  and  1899-1908,  after  Kullmer,  showing  Shift  of  Storm  Track. 

ally;  northward  the  decrease  is  very  rapid.  A  southerly  shift  of  the  storm  track  of  this 
region  would  cause  a  decrease  in  storm  frequency  in  the  squares  just  north  of  the  center 
of  the  curve,  which  is  seen  to  be  the  case  in  the  map  for  the  years  1899-1908  as  compared 
with  the  earlier  one.  At  the  same  time  the  southward  movement  of  the  storms  would 
produce  increased  storm  frequency  south  of  the  former  mean  storm  track,  which  is  actually 
the  case,  as  appears  from  the  increase  of  103  in  the  New  York  square.  Under  such  circum¬ 
stances  a  double  maximum  might  perhaps  be  produced  in  this  fashion.  Suppose  that  in 
the  earher  of  our  two  periods  the  curve  of  the  mean  storm  track  were  tangent  to  the  parallel 
of  latitude  47.5°  N.  which,  of  course,  is  the  mean  latitude  of  the  tier  of  squares  45°  to  50°  N. 

Being  tangent  to  this  parallel  at  the  most  southerly  swing  of  the  track  and  also  at  the  point 


202 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  greatest  storm  frequency,  we  should  clearly  get  a  single  maximum.  If,  however,  the 
mean  track  were  to  swing  somewhat  farther  south,  so  that  at  the  extreme  southern  limit 
(where,  as  before,  storms  were  most  frequent)  it  touched  latitude  46°,  it  would  cut  the 
parallel  of  47.5°  in  two  places.  As  46°  is  not  the  median  line  of  any  set  of  squares,  we 
should  not  have  any  maximum  corresponding  to  it,  but  we  should  have  a  double  maximum 
in  the  tier  of  squares  having  47.5°  as  their  median  line. 

Let  us  turn  now  to  the  question  of  how  far  the  apparent  increase  in  storm  frequency 
during  the  later  as  compared  with  the  earlier  of  our  two  periods  is  genuine.  The  total 
number  of  observations  of  storms,  as  obtained  by  adding  aU  the  numbers  on  each  of  the 
two  year-maps,  shows  that  the  total  frequency  for  the  later  period  is  17.4  per  cent  more  than 
for  the  earlier.  At  first  it  might  be  thought  that  this  is  due  merely  to  a  difference  either 


Fig.  65. — Changes  in  Storm  Frequency  by  Months  according  to  Longitude. 

Numerals  indicate  amount  of  increase  or  decrease  in  storm  frequency  in  the  given  longitude  for  each  month.  Lines  drawn  around  the 
areas  show  an  increase  of  over  40.  The  line  marked  “  zero  ”  indicates  no  change  in  frequency.  The  dotted  line  marked  "  maxi¬ 
mum  ”  indicates  maximum  increase. 

Fig.  66. — Changes  in  Storm  Frequency  by  Months  Irrespective  of  Longitude  and  Latitude. 

- =  Absolute  increase  in  storm  frequency  by  months. 

- =  Per  cent  of  increase.  Average  per  cent  equals  17.4. 

Fig.  67.^ — Changes  in  Storm  Frequency  by  Months  according  to  Longitude  in  Latitude  50°  to  55°. 

in  the  observational  material  or  in  the  way  in  which  it  has  been  treated.  Closer  inspection, 
however,  seems  to  show  that  this  is  not  the  case.  If  it  were  the  case,  we  should  expect  to 
find  that  the  increase  indicated  by  the  later  figures  is  distributed  somewhat  uniformly  over 
the  whole  country,  and  in  each  of  the  different  months.  In  order  to  test  this  I  have  plotted 
the  total  increases  in  storm  frequency  for  each  month  of  the  year  in  the  solid  line  of  figure 
66  and  the  percentage  of  increase  by  a  broken  line.  It  is  evident  that  the  increase  in  storm 
frequency  has  varied  from  7.5  per  cent  in  some  months  to  30  per  cent  in  others.  Moreover, 
the  curve  shows  a  seasonal  variation  with  two  periods  of  minimum  increase  in  the  late 
winter  and  late  summer,  and  two  of  maximum  increase  centering  approximately  in  May 
and  December.  In  addition  to  this,  I  have  plotted  the  increase  and  decrease  for  each 
month  of  the  year  in  each  north  and  south  colunm  of  5°  square,  as  is  shown  in  figure  65. 
Here  it  appears  that  the  lines  of  no  increase  and  of  maximum  increase  both  shift  eastward 
or  westward  according  to  the  seasons,  being  farthest  to  the  west  toward  the  end  of  the 
winter  and  early  in  the  fall,  at  about  the  time  when  the  greatest  increase  in  storm  frequency 


THE  SHIFTING  OF  CLIMATIC  ZONES, 


203 


takes  place.  If  the  increase  in  storm  frequency  for  a  single  tier  of  squares  (that  is,  for 
those  between  two  parallels  of  latitude  5°  apart)  is  plotted,  a  similar  phenomenon  is  ob¬ 
served  in  the  case  shown  in  figure  67,  where  the  increase  or  decrease  in  latitude  50°  to  55° 
has  been  plotted.  Here  again  the  curves  are  roughly  parallel  to  those  of  figure  66,  a 
phenomenon  whose  significance  is  not  apparent,  but  which  seems  worthy  of  study.  In 
latitude  45°  to  50°,  however,  as  appears  in  figure  68,  the  increase  or  decrease  in  storm 
frequency  assumes  a  character  entirely  different  from  that  farther  north.  The  diagram 
shows  a  peculiar  curved  area  of  decrease  and  a  diagonal  distribution  of  increase  with  a 
maximum  in  the  east  centering  during  the  month  of  March.  The  diagrams  of  this  same 
phenomenon  for  the  other  tiers  of  latitude  show  an  equally  variant  distribution,  as  may  be 
seen  in  part  in  figures  69  and  70. 


Fig.  68. — Changes  in  Storm  Frequency  by  Months  according  to  Longitude  in  Latitude  45°  to  50°. 

Finally,  the  last  diagram,  figure  71,  presents  a  summary  of  the  absolute  differences  in 
the  number  of  recorded  passages  of  storms  during  the  earlier  and  later  periods  for  each 
square  of  the  map.  The  appearance  of  the  map  varies  little,  whether  absolute  differences 
are  used,  as  in  figure  71,  or  percentage  differences.  This  map  offers  an  interesting  answer 
to  the  question  whether  the  differences  between  the  maps  (as  compiled  by  Dunwoody  in 
the  period  from  1878  to  1887  and  by  myself  for  the  period  from  1899  to  1908)  are  due 
merely  to  differences  in  method  and  in  observational  material  or  to  actual  differences  in 
the  number  of  storms.  On  the  map  I  have  indicated  the  barometric  stations  in  western 
Canada  which  were  used  for  the  earlier  period:  Fort  Rae,  Edmonton,  Calgary,  Medicine 
Hat,  and  Qu’Appelle.  It  will  be  seen  that  in  the  square  where  the  greatest  increase  in  storm 
frequency  is  noted  there  were  three  stations  during  the  earlier  period,  which  would  seem  to 
cover  that  region  sufficiently.  This  renders  strongly  probable  the  conclusion  that  the 
increases  and  decreases  shown  in  the  various  parts  of  the  map  are  real — in  great  part  at 
least.  It  is  also  noticeable  that  the  eastern  area  of  decreased  frequency  hes  directly  north 
of  the  area  where  the  munber  of  storms  is  greatest,  which  is  what  would  be  expected  if 
the  ideal  storm  track  (that  is,  the  mean  of  all  tracks  for  a  given  period)  had  been  shoved 
southward  and  westward.  Concordant  with  this  is  the  marked  increase  in  frequency  in 
the  southwest  and  south.  Taken  as  a  whole  it  appears  as  if  we  had  an  area  of  increased 


204 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


storm  frequency  sweeping  in  a  great  arc  from  northwestern  Canada  down  across  the 
Rocky  Mountain  region  to  Denver  and  Texas,  thence  eastward  through  Louisiana,  and 
up  the  Atlantic  coast  to  Maine.  This,  it  will  be  seen,  is  roughly  parallel  to  the  mean 


105  100  95  90  85  80  75  70  65 


Fig.  69. — Changes  in  Storm  Frequency  by  Months  according 
to  Longitude  in  I^atitude  30-35°. 


Fig.  70. — Changes  in  Storm  Frequency  by 
Months  according  to  Longitude  in  Lati¬ 
tude  25-30°. 


storm  track  as  defined  above,  although  much  more  curved  than  that,  and  lies  in  exactly  the 
place  where  we  should  expect  an  increase  if  the  track  had  been  shoved  southward. 

In  addition  to  the  points  already  mentioned,  there  is  another  and  wholly  different 
aspect  of  the  shift  of  the  storm  track  to  which  attention  should  be  called.  The  general 


Fig.  71.— Summary  of  Differences  in  Storm  Frequency,  1878-1887  and  1899-1908. 


conclusion  drawn  from  the  maps  seems  to  be  that  there  has  been  a  shght  southerly  and 
westerly  shift  of  the  storm  track  in  the  United  States  in  the  interval  of  twenty-one  years. 
In  this  same  interval  the  magnetic  field  in  the  United  States  has  shown  a  similar  shift. 
In  discussing  the  mysterious  changes  in  the  secular  variation  during  this  period.  Dr.  L.  A. 
Bauer  says  (Congressional  Documents  of  the  United  States,  vol.  5139,  p.  217): 


THE  SHIFTING  OF  CLIMATIC  ZONES. 


205 


“The  effect  of  these  complicated  changes  *  *  *  is  to  move  the  isogonic  lines  which  lie  east  of 
the  line  of  no  change  westward  and  those  west  of  the  no-annual-change-line  eastward,  or,  in  other 
words,  the  lines  are  being  crowded  together  from  both  sides  of  the  line  of  no  change.  This  effect 
considered  in  company  with  the  known  changes  in  dip  and  intensity  *  *  *  implies  that  the 
magnetic  pole  has  moved  during  the  past  twenty  years  chiefly  southward,  the  west  component  of 
motion  being  greatly  subordinate  to  the  southerly  one.” 

The  hypothesis  lies  near  that  the  storm  track  may  center  at  the  magnetic  pole  and  may 
move  with  the  magnetic  field.  If  such  an  hypothesis  can  be  entertained,  the  agreement 
here  shown  may  be  considered  to  be  in  harmony  with  it. 

In  conclusion,  I  should  like  to  point  to  the  desirability  of  having  similar  maps  made  for 
Japan  and  Europe,  the  only  other  areas  of  high  storm  frequency  in  the  northern  hemisphere. 
Lack  of  opportunity  and  the  inaccessibility  of  the  material  have  made  it  impossible  to 
construct  these  maps,  but  they  are  necessary  in  order  to  give  us  a  true  insight  into  the 
shift  of  the  storm  track.  In  constructing  such  maps  or  in  making  others  of  the  United 
States,  it  is  particularly  desirable  that  areas  of  less  than  5°  square  should  be  employed, 
in  order  to  bring  out  greater  detail.  Moreover,  a  single  year  should  be  the  unit,  and  the 
maps  for  single  years  should  be  compared  or  combined  bj^  the  use  of  overlapping  means  in 
such  a  way  as  to  determine  whether  the  location  of  storms  varies  from  times  of  maximum 
to  those  of  minimum  sun-spots.* 


This  brings  us  to  the  end  of  Professor  Kullmer’s  contribution.  Its  main  significance 
hes  in  the  fact  that  the  average  storm  followed  a  course  slightly  farther  south  and  west 
during  the  period  from  1899  to  1908  than  during  the  period  from  1878  to  1887.  To 
put  the  matter  in  another  way,  between  the  times  of  the  two  maps  the  zone  of  prevailing 
westerly  storms  moved  very  slightly  equatorward  from  its  earlier  position.  I  would  not 
be  understood  as  magnifying  the  slight  difference  between  the  two  maps.  Doubtless 
conditions  may  soon  once  more  become  the  same  as  they  were  during  the  period  covered 
by  Dunwoody’s  map,  and  there  is  no  reason  to  suppose  that  any  great  change  has  taken 
place.  The  important  point  is  that  here  we  have  direct  evidence  that  the  cHmatic  zones  of 
the  world  are  at  the  present  day  subject  to  minor  shif tings  back  and  forth,  and  that  these 
shiftings  on  a  small  scale  produce  the  results  which  our  assumed  larger  and  more  prolonged 
shiftings  appear  to  have  produced  upon  a  really  important  scale.  Meteorologists  almost 
universally  recognize  the  fact  of  such  minor  shiftings,  but  it  is  valuable  to  have  the  matter 
definitely  recorded  in  maps  which  can  readily  be  compared. 

We  have  now  seen  that  whether  single  years  or  longer  periods  such  as  decades  be  taken 
as  our  unit  of  time,  the  location  of  the  storm  tracks  shows  a  tendency  to  vary.  Let  us  now 
consider  the  same  question,  using  a  time  unit  of  much  greater  length. 

In  discussing  the  changes  of  climate  which  appear  to  have  taken  place  in  Asia  I  have 
elsewhere  shown  that  they  appear  to  be  of  the  same  nature  as  those  of  the  glacial  period, 
the  difference  being  one  of  degree,  not  kind.  In  the  western  hemisphere  the  evidence  points 
to  the  same  conclusion.  Hence  it  will  be  of  value  to  consider  some  of  the  latest  results  of 
researches  upon  the  conditions  of  glaciation  in  polar  regions  at  the  present  time.  These 
results  have  been  gathered  into  convenient  form  by  Professor  W.  H.  Hobbs,  in  his  book 
upon  “Glaciers,”  a  volume  which  contains  a  large  number  of  valuable  facts  as  well  as  some 
suggestive  theories.  To  meteorologists  and  glaciologists  one  of  the  surprising  results  of 
recent  explorations  of  Greenland  and  the  Antarctic  continent  has  been  the  discovery  that 

*  Since  this  chapter  was  in  print,  Professor  Kullmer  has  constructed  year  maps  of  the  storm  frequency  of  the 
United  States  from  1874  to  1912,  and  of  Europe  from  1876  to  1891,  the  only  period  for  which  data  are  available. 
These  maps  are  on  the  basis  of  areas  2.5°  in  latitude  by  5°  in  longitude.  They  confirm  the  conclusions  here  set 
forth  as  to  the  shifting  of  the  storm  track,  and  also  show  that  there  is  a  distinct  and  unmistakable  relatiori  between 
the  location  and  number  of  storms  on  the  one  hand  and  the  number  of  sun-spots  on  the  other,  (bee  page  25o.) 


206 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


these  ice-capped  areas  are  regions  of  high  rather  than  of  low  pressure.  Previously  it  had 
been  supposed  that  the  general  low  pressure  which  appears  to  become  more  and  more  pro¬ 
nounced  as  one  goes  poleward  prevails  over  all  lands  where  continental  ice-sheets  now 
exist.  It  was  thought  that  only  in  this  way  could  sufficient  precipitation  be  obtained  to 
support  the  great  ice-fields  and  send  out  the  thousands  of  bergs  and  floes  which  wreck 
our  ships. 

As  soon  as  explorers  began  to  study  the  winds  of  ice-capped  regions  with  any  care, 
however,  they  discovered  that  the  prevailing  movement  of  the  air  is  strongly  outward. 
At  times  it  may  be  reversed,  but  not  for  long.  This  means,  apparently,  that  high  barometric 
pressure  prevails  in  the  interior  and  is  busily  forcing  the  air  outward  except  at  times  when 
some  general  disturbance  upsets  the  normal  conditions.  This  is  what  would  naturally  be 
expected,  since  vast  areas  of  snow  are  bound  to  be  extremely  cold  and  hence  are  likely  to 
induce  high  barometric  pressure.  Hitherto,  however,  it  has  generally  been  supposed  that 
such  almost  continuous  high  pressure  could  not  characterize  these  regions  because  there 
would  be  no  way  of  obtaining  precipitation.  Hobbs  has  attempted  to  explain  this  by  an 
ingenious  hypothesis  which  holds  that,  under  the  peculiar  conditions  of  glaciation  and  of 
the  newly  discovered  inversion  of  atmospheric  temperature  at  high  levels,  fine  crystals  of 
snow  can  be  deposited  even  when  the  barometer  is  high  and  the  upper  air  clear.  Whether 
his  theory  is  sound  or  not  can  not  here  be  discussed,  but  it  seems  at  least  to  be  worthy  of 
careful  consideration.  Its  chief  value,  however,  lies  in  its  emphasis  of  the  fact  that  regions 
of  continental  glaciation  appear  to  be  areas  of  high  pressure.  This  being  so,  an  increase 
in  the  area  of  continental  glaciation  would  mean  an  increase  in  the  area  of  permanent  high 
pressure.  At  the  height  of  a  glacial  epoch  high  pressure  would  prevail  throughout  the  year 
over  most  of  the  northeastern  part  of  North  America,  and  over  northwestern  Europe. 
If  other  conditions  remained  in  general  the  same  as  at  present,  the  barometric  gradients 
from  the  great  glaciated  areas  of  high  pressure  to  the  low  areas  of  the  oceans  and  of  equa¬ 
torial  regions  would  be  steeper  than  now.  Hence  the  winds  would  acquire  great  strength, 
storms  would  be  more  numerous  than  now,  and  they  would  follow  more  southerly  courses. 
Forced  far  to  the  south  by  the  great  continental  high  areas  both  in  northeastern  America 
and  northwestern  Europe,  they  would  probably  swing  down  into  the  Gulf  of  Mexico  or 
the  Sahara  Desert,  as  the  case  might  be,  and  the  climates  of  those  southerly  regions  would 
partake  of  the  unstable  and  stimulating  nature  which  to-day  is  so  characteristic  of  the  parts 
of  North  America  and  Europe  where  the  world’s  most  progressive  races  dwell. 

If  we  are  right  in  supposing  that  the  climatic  changes  of  which  we  seem  to  have  foimd 
evidence  during  historic  times  are  of  the  same  nature  as  those  of  the  glacial  period,  we  can 
readily  see  how  in  the  days  of  Yucatan’s  glory  the  storminess  now  characteristic  of  the 
United  States  may  have  prevailed  farther  south.  At  all  seasons,  but  especially  during 
the  winter,  cyclonic  disturbances  were  probably  more  frequent  and  severe  than  now,  the 
winds  presumably  blew  more  forcibly,  and  the  minimum  temperature  of  Yucatan  may  have 
fallen  as  low  as  freezing  instead  of  only  to  50®.  The  effect  which  such  a  southward  shifting  of 
the  stormy  belt  would  have  upon  precipitation  deserves  careful  consideration.  At  present 
the  “northers”  bring  very  little  rain  to  Yucatan,  since  they  are  cold  winds  moving  rapidly 
toward  warmer  regions.  Therefore  their  capacity  for  moisture  increases  and  they  are  not 
likely  to  produce  much  rain.  Neither  their  frequent  prevalence  nor  the  general  shoving 
southward  of  the  dry  subtropical  zone  would  probably  have  much  effect  upon  the  winter 
rainfall  of  the  dry  northern  parts  of  Yucatan,  but  might  much  diminish  that  of  the 
forested  regions.  This  is  because  the  winter  rainfall  is  here  due  to  the  trade  winds.  If 
cyclonic  storms  came  farther  south  than  at  present,  they  would  destroy  the  trade  winds 
in  this  latitude  and  would  allow  them  to  prevail  only  in  regions  farther  south.  Hence 
there  would  not  be  any  steady  winds  blowing  in  from  the  sea  through  the  winter  and  causing 
abundant  precipitation.  This  would  give  rise  to  a  dry  season  longer  and  more  intense  than 


THE  SHIFTING  OF  CLIMATIC  ZONES.  207 

that  which  now  prevails  there  and  would  thus  tend  to  cause  jungle  to  take  the  place  of 
forests. 

The  effect  of  such  a  change  upon  the  summer  rains,  on  the  other  hand,  can  not  easily 
be  determined.  Possibly  the  general  strengthening  of  the  winds  would  bring  the  equa¬ 
torial  rains  farther  north  than  is  now  the  case,  or  would  at  least  make  them  more  abundant. 
It  is  equally  possible  that  the  shoving  southward  of  the  zone  of  storms  would  be  as  prom¬ 
inent  a  feature  in  summer  as  in  winter,  and  hence  that  the  equatorial  rains  would  not 
come  so  far  north  as  at  present.  A  possible  test  of  this  matter  lies  in  a  comparison  of  the 
curve  of  the  sequoia  in  California  with  the  fluctuations  of  the  lakes  around  the  City  of 
Mexico,  but  the  data  are  so  imperfect  that  it  is  not  conclusive.  The  California  growth 
represents  the  variations  in  a  purely  winter  type  of  rainfall  characteristic  of  the  zone  of 
prevailing  westerlies.  The  fluctuations  of  the  lakes  of  Mexico,  on  the  other  hand,  are  due 
to  a  rainfall  which  comes  almost  entirely,  but  not  wholly,  from  May  to  October,  and  is 
largely  of  the  equatorial  type.  Hence,  if  a  strengthening  of  the  earth’s  circulation  increases 
the  equatorial  rains  as  well  as  those  of  the  zone  of  westerlies,  we  should  expect  to  find  the 
Mexican  lakes  high  at  the  same  time  when  the  California  trees  grow  rapidly.  This  would 
not  necessarily  mean  that  in  summer  the  rains  of  the  equatorial  type  shifted  farther  north 
than  now,  although  this  is  a  possibility.  It  would  merely  indicate  that  the  more  rapid 
circulation  of  the  air  caused  the  equatorial  rains  to  be  heavier  than  at  present. 

With  this  in  mind  let  us  sum  up  the  variations  of  the  lakes,  as  set  forth  in  Chapter  X, 
and  compare  them  with  the  curve  of  the  sequoia  as  given  in  figure  72.  Our  first  knowledge 
of  the  Mexican  lake  suggests  that  in  1325  a.  d.,  when  the  Aztecs  founded  the  City  of  Mexico, 
it  stood  quite  high.  At  this  time  the  California  trees  were  growing  very  rapidly  and  grew 
still  more  rapidly  during  the  succeeding  decade.  Then  their  growth  decreased  until  about 
1420.  Thereafter,  for  the  space  of  forty  years,  the  growth  of  the  trees  remained  practi¬ 
cally  stationary — or,  to  put  it  in  another  way,  a  climatic  change  markedly  checked  a 
previously  rapid  rate  of  decline,  but  did  not  succeed  in  reversing  it.  Just  what  happened 
in  Mexico  at  this  time  we  do  not  know.  It  merely  appears  that  during  the  forty  years  of 
the  change  in  California,  conditions  were  such  that  after  some  severe  floods  in  the  early 
years  of  the  reign  of  Montezuma,  the  Aztecs  were  at  length  led  to  build  the  first  dike  in 
1446.  The  history  of  the  inundations  of  Mexico  City  from  the  time  of  Montezuma  to 
1800  A.  D.  is  summed  up  in  table  10.  The  data  here  used  are  taken  partly  from  Humboldt, 
who  speaks  of  fourteen  chief  floods  between  the  time  of  Montezuma  and  his  own  day. 
The  chief  of  these,  which  occurred  in  1553,  1604,  and  1607,  are  mentioned  (it  will  be 
remembered)  by  Torquemada.  Certain  other  floods  are  mentioned  by  Cavo,*  whose 
work  terminates  with  the  year  1765.  From  this  work  Mr.  A.  F.  Bandolier  has  kindly 
gleaned  for  me  the  references  noted  in  the  table.  The  inundations  mentioned  only  by 
Cavo  are  less  important  than  those  mentioned  by  the  other  authorities. 

The  table  scarcely  requires  explanation,  but  a  few  words  as  to  the  general  course  of 
events  may  not  be  amiss.  After  the  time  of  Montezuma  the  growth  of  the  trees  fell  off 
at  a  very  rapid  rate,  and  from  about  1460  to  1490  we  find  them  growing  as  slowly  as  at 
any  known  period.  No  inundations  are  recorded  during  this  time,  but  Humboldt  tells 
us  that  the  Mexican  lakes  fell  to  so  low  a  level  that  the  city  suffered  much  distress  because 
canoes  laden  with  food  could  not  come  in  as  formerly  from  the  surrounding  country.  There¬ 
after  the  rate  of  growth  of  the  trees  increased  rapidly  until  about  1560,  and  in  this  period 
we  find  four  inundations,  the  last  of  which,  in  1553,  was  famous.  It  is  noteworthy  that  it 
occurred  at  about  the  time  when  the  trees  reached  their  maximum  rate  of  growth.  Next 
the  trees  fell  off  slightly  for  thirty  years,  approximately  from  1565  to  1595,  and  Mexico 
City  did  not  suffer  greatly,  although  one  inundation  of  no  great  note  occurred  in  1580. 
Then  the  growth  of  the  trees  increased  at  a  very  rapid  rate  during  the  decade  from  1600 


*  Les  Tres  Siglos  de  Mejico  (Jalapa,  1870,  edited  by  Carlos  Maria  de  Bustamentes). 


208 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA, 


to  1610,  and  at  this  same  time  Mexico  suffered  from  two  phenomenal  inundations.  There¬ 
after  there  came  a  brief  dry  period  in  Mexico  marked  by  drought  and  famine  in  1608  and 
again  in  1615.  This  does  not  appear  in  the  California  trees,  whose  growth  merely  ceases 
to  increase  in  rate,  but  still  remains  high.  It  is  quite  possible,  however,  that  these  par¬ 
ticular  years  were  bad  years  in  California,  but  that  their  effect  is  concealed  by  the  good 


Table  10. 


Year. 

Authority. 

1440(?) 

Torquemada . 

Humboldt. 

1498 

Humboldt . 

1519 

Do . , . 

1523 

Cavo,  p.  25 . 

1553 

Humboldt . 

Torquemada. 

Cavo,  p.  109. 

1580 

Humboldt . 

1604 

Do . 

Torquemada. 

1607 

Humboldt . 

Torquemada. 

Cavo,  p.  162. 

1623 

Cavo,  p.  175 . 

1629 

Humboldt;  Cavo,p.l83. 

1645 

Cavo,  p.  196 . 

1648 

Humboldt . 

1675 

Do . 

1691 

Cavo,  p.  233 . 

1697 

Cavo,  p.  240  . 

1707 

Humboldt . 

1732 

Do . 

1748 

Do . 

1762 

Cavo,  p.  293  . 

1772 

Humboldt . 

1795 

Do . 

Conditions  in  Mexico  City. 


Great  inundation. 


Inundation.  This  has  no  great  sig¬ 
nificance,  because  it  was  due  to  the 
mistaken  policy  of  turning  the 
Huitzilopoche  River  into  Lake 
Tezcuco. 

Inundation . 

Do . 

A  famous  inundation.  According  to 
Cavo  a  drought  was  broken  by  a 
violent  rain  that  lasted  not  quite 
24  hours  and  inundated  the  whole 
valley  of  Mexico.  Such  inunda¬ 
tions  (according  to  Bandolier)  were 
at  that  time  frequent  and  were  not 
regularly  recorded  on  account  of 
being  looked  upon  as  a  common 
occurrence. 

Inundation . 

Famous  inundation . 

Great  inundation . 

Inundation  in  December . 

Inundation.  Great  rains . 

Inundation . 

Do . 

Do . 

Inundation  and  also  heavy  frosts 
unusually  early. 


Inundation . 

Do . 

Do . 

Do . 

Overflow  of  Lake  of  Mexico , 

Inundation . 

Do . 


Conditions  of  tree  growth  in  California. 

Relation  of  Mexican  lakes 
and  California  trees. 

Slight  decrease  in  rate  of  growth  com- 

Neutral. 

pared  with  previous  decade,  but 
during  this  general  period  a  very  great 
jdecrease  changes  to  essential  uni¬ 
formity. 

Slow,  but  steadily  increasing . 

Agreement. 

Medium  in  amount  and  rapidly  in- 

Do. 

creasing. 

Medium  and  only  slightly  increasing  . . 

Neutral. 

Rapid  with  great  increase . 

Marked  agreement. 

Medium  with  moderate  decrease . 

Disagreement. 

Rapid  growth  and  great  increase . 

Marked  agreement. 

Do . 

Do. 

Rapid,  but  beginning  to  decrease . 

Neutral. 

Do . 

Do. 

Medium,  but  with  slight  increase . 

Do. 

Do . 

Do. 

Rapid  and  increasing . 

Agreement. 

This  decade  was  characterized  by 

Neutral. 

marked  decrease,  but  at  its  beginning 
the  growth  was  very  rapid,  so  that  it 
is  impossible  to  determine  whether  the 
first  year  of  the  decade  was  character¬ 
ized  by  slow  growth  or  fast. 

Same  as  preceding,  but  as  this  year 

Disagreement. 

comes  toward  the  end  of  the  decade 
it  probably  should  be  counted  as 
distinct  disagreement. 

Slow  with  rapid  decrease . 

Pronounced  disagreement. 

Moderately  rapid,  and  with  rapid  in- 

Agreement. 

crease. 

Rapid  with  marked  increase . 

Pronounced  agreement. 

Fairly  high,  but  rapidly  decreasing. 

Disagreement. 

This  case  may  be  like  that  of  1691, 
but  it  is  better  to  reckon  it  as  dis¬ 
agreement. 

Low  but  with  a  distinct  rise . 

Agreement. 

Moderately  rapid  with  great  increase  . . 

Do. 

The  following  occurrences  of  dry  times  should  be  mentioned  in  connection  with  the  table:  Cavo  (p.  109)  states 
that  the  violent  floods  of  1553  followed  a  drought,  but  it  is  not  evident  whether  the  drought  was  of  any  importance. 
In  1608  (p.  164)  after  the  great  floods  of  1604  and  1607,  he  speaks  of  another  drought  followed  by  the  receding  of  the 
lake  in  1609,  while  in  1615  (p.  171)  he  records  a  drought  and  famine.  Both  of  these  must  be  regarded  as  distinct  dis¬ 
agreements.  In  1750  (p.  287)  he  records  famines  in  northern  Mexico,  but  good  crops  south  of  Guanajuato.  This 
comes  at  the  end  of  a  time  of  rapidly  increasing  growth  in  the  trees,  but  is  not  distinct  enough  to  be  counted,  except 
as  neutral. 


years  before  and  after  them.  In  the  next  decade,  1621  to  1630,  we  find  the  trees  still 
growing  rapidly,  and  in  Mexico  City  there  were  two  inundations.  Thereafter  the  trees 
decline,  but  only  a  little.  In  the  decade  from  1641  to  1650  their  growth  revives  very 
slightly,  and  in  Mexico  there  were  two  inundations,  neither  of  them  of  the  first  importance. 


THE  SHIFTING  OF  CLIMATIC  ZONES. 


209 


In  table  10  these  cases  are  marked  as  neutral,  but  in  reality  it  might  be  fair  to  mark 
them  as  showing  agreement.  The  next  event  in  the  history  of  the  trees  is  an  increase 
in  the  rate  of  growth  lasting  for  thirty  years.  During  this  period  a  tunnel  carried  off  the 
surplus  waters  of  the  lakes,  and  therefore  no  inundations  are  recorded,  even  though  it  is 
possible  that  some  would  otherwise  have  occm-red.  In  1675,  at  the  time  when  the  rate  of 
growth  of  the  trees  was  increasing  most  rapidly,  a  flood  is  said  to  have  so  injured  the  tunnel 


Fig.  72. — Changes  of  Climate  in  California  for  2,000  Years. 

This  figure  is  the  same  as  the  part  of  figure  50  after  100  n.  c.,  but  is  plotted  with  a  threefold  greater  vertical  scale. 


that  it  caved  in.  Nevertheless,  Mexico  City  was  not  flooded,  probably  because  even  after 
the  collapse  of  the  tunnel  it  still  functioned.  In  1697  and  again  in  1707  two  inundations 
occurred,  which  are  markedly  out  of  harmony  with  the  apparent  rainfall  in  California.  About 
1730  the  trees  again  rapidly  increased  their  rate  of  growth,  and  Mexico  suffered  from 
two  inundations.  It  is  probable  that  a  somewhat  general  increase  of  rainfall  stimulated 
the  Mexicans  once  more  to  attempt  to  get  rid  of  the  water,  for  in  1755  a  long  series  of 
schemes  for  draining  the  lakes  culminated  in  a  really  successful  tunnel.  After  this  time 
the  increasing  number  of  artificial  constructions  makes  it  impossible  to  judge  of  the  climate 
from  the  fluctuations  of  the  lakes.  Of  the  three  inundations  recorded  between  1750  and 
1800  the  first  occurred  in  a  decade  when  the  trees  showed  a  marked  decrease  in  growth, 
whereas  the  other  two  occurred  at  a  time  when  the  trees  increased  their  rate  of  growth. 

To  sum  up  the  matter  we  find  records  of  twenty  inundations,  great  and  small,  between 
the  times  of  Montezuma  and  Humboldt.  All  the  great  inundations  took  place  at  times 
when  the  trees  were  growing  rapidly.  Including  great  and  small,  we  find  four  cases  where 
there  is  a  disagreement  between  the  trees  and  the  lakes,  seven  in  which  the  matter  is  open 
to  question  (since  the  data  for  individual  years  are  not  available  for  comparison),  and  ten 
showing  agreement.  The  suggestive  point  about  the  whole  matter  is  that,  in  spite  of  minor 
disagreements,  the  main  eras  of  high  water  in  the  lakes  seem  to  correspond  with  periods  of 
rapid  or  increasing  growth  in  the  trees.  So  far  as  this  single  line  of  evidence  is  concerned, 
it  seems  to  suggest  that  when  the  winter  rainfall  increases  in  the  zone  of  prevailing  westerlies, 
the  summer  rainfall  increases  on  the  borders  of  the  equatorial  zone.  It  must  be  remem¬ 
bered,  however,  that  in  some  cases,  such  as  1623,  the  floods  were  due  to  winter  rainfall, 
suggesting  that  winter  storms  came  farther  south  than  usual.  If  the  conclusion  here 
reached  is  really  true,  it  appears  that  at  certain  past  periods  not  only  Mexico  City  but  such 
places  as  Yucatan  probably  had  more  summer  rain  than  at  present,  while  during  the  winter 
not  only  did  all  parts  of  the  country  enjoy  greater  variations  of  temperature  than  is  now  the 
case,  but  the  parts  now  receiving  rains  from  the  trade-winds  were  drier  than  to-day,  and 
hence  were  covered  with  jungle  and  bush  instead  of  forest  and  jungle. 

How  great  a  direct  effect  upon  the  inhabitants  may  have  been  produced  by  these  in¬ 
ferred  climatic  changes  it  is  hard  to  tell.  In  a  later  volume  I  hope  to  discuss  this  question 
fully  and  to  present  the  results  of  a  large  series  of  observations  upon  the  state  of  human 
activity  under  widely  different  climatic  conditions.  The  results  there  to  be  given  will 
be  based  upon  absolute  mathematical  measurements  of  human  efficiency.  At  present, 
however,  we  must  be  content  with  a  single  example  which  illustrates  one  of  the  important 

15 


210 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


ways  in  which  climatic  variations  may  produce  their  effects.  During  my  visit  to  Yucatan 
I  again  and  again  inquired  of  all  sorts  of  people  as  to  the  kind  of  weather  when  the  modern 
Yucatecos  work  most  vigorously.  The  universal  answer  was  on  “fresh’'  days,  which 
means  the  coolest  days  that  Yucatan  ever  enjoys.  When  I  put  this  question  to  Mr.  E.  H. 
Thompson  he  answered  it  as  did  every  one  else,  and  then  with  characteristic  energy  went 
out  early  the  next  morning  to  interview  some  of  the  best-informed  men  among  the  Indians. 
They,  too,  gave  the  usual  answer,  and  then,  thinking  it  over  a  little  more,  added,  “Yes, 
the  Mayas  work  hardest  when  there  is  a  fresh  spell;  the  morning  after  a  ‘norther’  is  the 
time;  then  the  air  is  cool  and  clear,  and  the  women  bake  the  tortillas  much  more  quickly 
than  usual,  so  that  we  get  away  to  work  early.”  Nothing  for  to-day,  as  we  have  said,  is 
ever  prepared  yesterday  in  Yucatan,  and  so  in  the  morning  the  men  always  have  to  wait 
until  the  women  have  ground  some  corn,  mixed  the  batter,  and  cooked  some  thin  tortillas 
on  a  flat  sheet  of  iron.  Therefore  the  husbands,  not  being  able  to  depart  until  the  day’s 
supply  of  bread  is  ready,  take  especial  note  of  the  speed  with  which  it  is  prepared.  Perhaps 
this  may  seem  a  trivial  thing  to  mention  in  connection  with  a  great  problem  like  that  of 
the  cause  of  the  rise  and  fall  of  nations,  but  it  illustrates  the  fact  that  among  the  physical 
stimuli  which  may  control  human  efficiency  none  is  more  potent  than  climate.  Perchance, 
if  Yucatan  had  a  norther  every  three  days  instead  of  only  at  rare  intervals,  the  energy  of 
the  population  might  be  greatly  increased.  If  the  northers  were  so  cold  that  the  temper¬ 
ature  fell  to  freezing,  as  it  does  at  Canton  in  China,  scarcely  farther  from  the  equator  than 
is  Yucatan,  the  present  Yucatecos  might  in  time  become  as  efficient  as  the  Cantonese. 
With  our  present  scanty  knowledge  of  the  exact  effects  of  varying  conditions  of  temperature, 
pressure,  humidity,  and  the  like  upon  man’s  vital  processes,  it  would  be  rash  to  say  how 
far  the  difference  between  the  Yucatan  of  the  past  and  that  of  the  present  may  be  due  in 
part  to  climatic  causes.  This  much,  however,  can  be  safely  said:  if  the  shifting  of  zones 
has  taken  place  in  any  such  way  as  we  have  inferred,  the  peculiar  contrast  between  the 
wonderfully  progressive  people  who  once  dwelt  in  Yucatan  and  the  indolent  present 
inhabitants  is  much  less  inexplicable  than  is  now  the  case. 


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HUNTINGTON 


PLATE  10 


A.  The  church  of  Esquipulas,  representing  the  best  Spanish  architecture  m  Guatemala. 

B.  The  rivervvard  side  of  the  main  citadel  at  Copan.  On  the  extreme  right,  directly  under  the  arrow,  layers  of 

alluvial  deposits  can  be  seen  underlyi.ig  artificial  constructions.  The  wall  of  figure  73  lies  on  the  extreme 
left. 


CHAPTER  XVII. 

GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION.* 

When  the  final  revision  of  this  volume  was  made  in  January  and  February  1913,  the 
author  felt  that  his  conclusions  as  to  the  torrid  zone  required  further  testing.  The  logical 
place  for  such  a  test  was  Guatemala,  since  there  the  Mayas  brought  to  a  culmination  the 
highest  civilization  of  native  American  origin.  Accordingly  in  March  and  April  1913, 
independently  of  the  Carnegie  Institution,  he  spent  about  four  weeks  in  that  country  or 
on  its  borders  in  British  and  Spanish  Honduras.  In  previous  chapters  four  chief  lines  of 
evidence  have  been  used,  namely,  alluvial  terraces,  changes  in  lakes,  the  distribution  of 
ruins,  and  the  rate  of  growth  of  trees.  Only  two  of  these,  terraces  and  ruins,  are  of  much 
significance  in  Guatemala.  Lakes,  to  be  sure,  are  numerous,  and  of  great  beauty,  but  all 
have  outlets,  and  are  of  interest  chiefly  in  relation  to  the  volcanoes  which  seem  in  several 
cases  to  have  formed  them  by  closing  deep  valleys  which  previously  opened  toward  the 
Pacific.  The  trees  of  Guatemala  are  of  course  abundant,  but  are  of  little  use  for  our 
purpose.  Those  growing  in  the  tropical  forests  of  the  lowlands  are  often  of  large  size  and 
perhaps  of  considerable  age,  but  constant  moisture  renders  their  rings  too  indefinite  to  be 
rehable.  The  pines  of  the  highlands,  on  the  other  hand,  although  possessed  of  definite 
annual  rings  because  of  the  pronounced  contrast  between  the  wet  and  dry  seasons,  appear 
rarely  to  be  over  100  years  old,  and  hence  are  of  little  importance.  Terraces  and  ruins, 
on  the  other  hand,  are  not  only  abundant,  but  they  fortunately  lie  sometimes  in  intimate 
juxtaposition. 

Our  consideration  of  the  terraces  and  ruins  will  be  clearer  if  preceded  by  a  brief  descrip¬ 
tion  of  the  country  as  a  whole.f  From  northeast  to  southwest,  Guatemala,  together  with 
British  Honduras,  which  for  convenience  I  shall  treat  as  if  it  were  part  of  the  same  country, 
consists  of  a  young  Atlantic  plain,  a  system  of  mature  mountains,  a  young  volcanic  plateau, 
and  a  young  Pacific  plain.  The  Atlantic  plain  is  merely  a  continuation  of  that  of  Mexico, 
which,  after  expanding  into  the  peninsula  of  Yucatan,  diminishes  in  width  until  it  is 
finally  drowned  beneath  the  sea  east  of  the  Cockscomb  Mountains  of  southern  British 
Honduras.  The  whole  plain  is  densely  forested,  intensely  fever-stricken,  and  almost 
uninhabited.  A  few  mahogany  cutters  form  villages  along  its  winding  rivers,  a  small 
number  of  cattle  are  fattened  in  grassy  savannas  where  an  excess  of  sand  or  water  prevents 
the  growth  of  trees,  and  a  few  primitive  Indians  cultivate  isolated  patches  of  land  here  and 
there  in  its  remote  recesses.  As  a  whole  it  is  one  of  the  world’s  most  scantily  populated 
and  least-known  districts. 

The  mature  mountains  consist  of  a  series  of  ranges  of  distorted  strata  running  nearly 
east  and  west  and  rising  from  5,000  to  10,000  feet  above  the  sea.  Their  seaward  portions, 
where  exposed  to  the  northeast  trades,  are  heavily  forested  and  feverish,  and  therefore 
almost  uninhabited.  The  higher  portions,  and  also  those  of  the  lower  mountains  which 
are  not  kept  continually  wet  by  the  trade  winds,  are  covered  with  pines  and  support  a 
moderate  number  of  people.  Most  of  the  population,  however,  is  concentrated  in  deep, 
dry  valleys  or  basins  such  as  those  of  Coban  and  Zacapa,  which  lie  among  the  mountains 
and  are  thus  protected  from  excessive  moisture. 

*  This  chapter,  in  a  somewhat  changed  form,  is  reprinted  from  the  Transactions  of  the  American  Philosophical 

Society,  vol.  lii.  No.  211,  pp.  467-487,  Philadelphia,  1913. 
t  See  map,  p.  174. 


211 


212 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


At  their  western  end  the  old  mountain  ranges  are  buried  under  vast  deposits  of  volcanic 
tuff  forming  a  broad  plateau.  On  the  western  border  of  this  a  line  of  splendid  volcanoes, 
10,000  to  13,500  feet  high,  extends  along  the  Pacific  side  of  the  country  at  a  distance  of 
30  to  40  miles  from  the  coast.  The  plateau  itself,  at  an  altitude  of  from  5,000  to  8,000 
feet  above  the  sea,  is  relatively  flat,  although  divided,  as  it  were,  into  terraces  at  various 
elevations.  It  would  be  easy  to  traverse  except  that  it  is  frequently  cut  by  deep  '  ‘  barancos” 
or  canyons  with  nearly  vertical  sides.  In  a  state  of  nature  most  of  the  plateau  would  be 
covered  with  an  open,  grassy  pine  forest,  but  its  healthfulness  and  coolness  have  caused 
it  to  be  almost  entirely  cleared  and  to  be  the  home  of  one  of  the  densest  agricultural  popu¬ 
lations  to  be  found  in  any  part  of  the  world. 

Southwest  of  the  plateau  the  lower  slopes  of  the  volcanoes  are  densely  forested  and 
feverish,  for  rain  falls  whenever  the  trade-winds  weaken  and  a  movement  of  the  air  takes 
place  from  the  Pacific.  Coffee  is  here  raised  on  a  large  scale,  but  w'ere  it  not  for  this  the 
population  would  be  relatively  scarce.  The  lower  edge  of  the  coffee  country  extends  into 
the  Pacific  plain.  While  the  volcanoes  were  building  up  the  plateau,  the  rivers  were  busily 
carrying  volcanic  materials  down  toward  the  Pacific  Ocean,  and  forming  a  smooth  pied¬ 
mont  plain  20  to  30  miles  wide.  The  inner  edge  of  the  plain  lies  in  the  zone  of  dense  jungle, 
500  to  1,000  feet  above  the  sea.  The  seaward  edge  is  relatively  dry  and  bears  a  wearisome 
growth  of  thick  bushes.  Everywhere  the  plain  is  unhealthful  and  sparsely  populated,  for 
in  the  rainy  seasons  its  flat  surface  holds  the  water  in  stagnant  swamps,  where  mosquitoes 
breed  by  the  milhon. 

Turning  now  to  the  terraces,  our  first  line  of  evidence  as  to  changes  of  chmate,  we  find 
an  interesting  contrast  between  the  Pacific  and  Atlantic  slopes.  On  the  Pacific  slope  I  saw 
more  or  less  of  at  least  a  dozen  small  river  systems,  some  in  their  head-waters  before  they 
had  passed  through  the  great  line  of  volcanoes,  and  some  farther  downstream.  None 
are  well  terraced  like  certain  valleys  in  southern  Mexico,  but  many  show  evidence  that  a 
terracing  process  has  not  been  wholly  absent.  On  the  river  between  Tecpam  and  Gaudines, 
for  instance,  the  valley  was  first  eroded  to  nearly  its  present  level,  was  then  filled  to  a  depth 
of  at  least  30  to  40  feet  with  coarse  alluvium,  and  has  since  been  re-excavated.  Before  the 
re-excavation  the  stream  was  displaced  to  one  side  of  the  valley,  so  that  when  it  began 
cutting  downward  it  soon  encountered  solid  rock.  In  this  it  has  cut  only  a  narrow  gorge, 
although  both  upstream  and  down  it  has  so  broadened  the  valley  floor  that  only  faint  traces 
of  terraces  are  seen.  Many  other  phenomena  indicate  that  as  a  rule  the  valleys  of  the 
Pacific  slope  have  recently  experienced  two  periods  of  terracing  and  that  the  terraces  occur 
both  above  and  below  the  volcanoes,  but  are  generally  better  developed  above.  As  might 
be  anticipated,  however,  the  evidence  is  not  strong,  partly  because  the  streams  fall  rapidly 
and  the  slopes  are  well  covered  with  vegetation,  and  still  more  because  where  volcanoes 
have  been  active  so  recently  it  would  be  idle  to  look  for  marked  chmatic  terraces  of  any 
great  age.  If  the  scanty  terraces  now  visible  are  of  climatic  rather  than  volcanic  origin, 
they  may  enable  us  to  date  various  events  in  the  volcanic  history  of  the  country.  For  our 
present  purpose,  however,  they  possess  no  special  importance. 

On  the  Atlantic  slope  the  case  is  far  different,  for  volcanic  action  either  ceased  long 
ago  or  never  prevailed,  and  large  areas  are  so  dry  that  almost  any  climatic  change  would 
have  an  appreciable  effect  upon  vegetation.  I  was  able  to  see  only  two  drainage  systems, 
those  of  the  large  Motagua  River  and  the  small  Santa  Toma  just  north  of  it.  They  suffice, 
however,  to  show  that  here,  just  as  in  southern  Mexico,  Arizona,  Persia,  and  many  other 
places,  the  most  recent  geological  times  have  been  characterized  by  at  least  four  terrace¬ 
making  epochs.  The  reasons  for  behoving  the  terraces  to  be  of  climatic  rather  than  of 
tectonic  origin  are  the  same  here  as  elsewhere.  The  very  fact  of  their  occurrence  here 
with  the  same  character  as  in  far- distant  regions  is  in  itself  a  strong  reason  for  assigning 
to  them  an  origin  of  world-wide  application,  such  as  climate,  rather  than  local  earth-move- 


GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION. 


213 


merits.  On  the  lower  Motagua  River,  in  the  wet  forested  country,  the  terraces  are  only 
slightly  developed,  but  may  be  seen  near  the  notable  ruins  of  Quirigua  and  elsewhere; 
on  the  dry  middle  course  of  the  river,  from  Zacapa  upward,  they  are  highly  developed; 
and  in  the  moderately  watered  regions  of  the  upper  course  they  are  also  well  developed. 
This  is  Hkewise  the  case  along  the  only  two  main  tributaries  which  I  saw,  the  Copan  and 
Chiquimula  branches,  which  join  the  main  river  at  Zacapa.  On  the  upper  river,  where 
it  is  crossed  by  the  road  from  S.  Toma  de  Chichestenango  to  S.  Cruz  de  Quichd,  there  is 
convincing  proof  that  the  terrace-making  process  consisted  of  both  erosion  and  deposition. 
Because  of  the  change  in  the  relative  positions  of  the  main  stream  and  a  tributary,  one  can 
see  an  old  channel  which  was  first  excavated  and  then  filled  with  gravel  to  a  depth  of  40 
to  50  feet  and  perhaps  more.  The  top  of  this  gravel  corresponds  with  a  well-developed 
terrace. 

The  Motagua  River,  flowing  from  high,  dry  regions  through  alternate  gorges  and  broad 
valleys,  is  the  kind  of  stream  that  might  be  expected  to  have  terraces  of  climatic  origin. 
Its  little  neighbor,  the  Santa  Toma,  on  the  other  hand,  is  of  quite  a  different  nature. 
It  is  a  short,  insignificant  stream  running  down  from  the  eastern  end  of  the  Sierra  de  las 
Minas,  between  the  large  Motagua  River  on  the  south  and  the  Rio  Dolce  on  the  north. 
Its  entire  course  appears  from  the  maps  to  be  not  over  30  miles,  and  all  of  it  apparently 
lies  among  dense  vegetation.  In  this  region,  in  contrast  with  the  youthful  coastal  plain 
of  Yucatan,  the  last  main  movement  of  the  land  seems  to  have  been  downward,  so  that 
the  inner  corner  of  the  Gulf  of  Honduras,  near  Puerto  Barrios  and  Livingstone,  presents 
a  strikingly  bold,  indented  coast  line  with  isolated  islands  and  deep  inlets.  This  movement, 
however,  occurred  long  ago  and  since  its  completion  a  long  period  of  comparative  stabihty 
has  allowed  large  deltas  to  be  formed.  In  ascending  the  Santa  Toma  River  one  traverses 
a  delta  for  perhaps  5  miles,  first  through  mangrove  swamps  and  then  through  the  ordinary, 
dense  tropical  forest.  A  small  terrace  appears  after  one  is  well  within  the  solid  portion  of 
the  delta;  farther  inland  it  becomes  higher,  and  where  the  delta  joins  the  hilly  old  land  at 
least  four  terraces  are  well  developed.  The  full  development  of  the  delta  and  the  apparent 
absence  of  any  signs  of  recent  upheaval  of  the  land  agree  with  the  lines  of  evidence  already 
cited  in  other  chapters  in  indicating  a  climatic  rather  than  tectonic  origin  of  the  terraces. 
If  this  be  correct,  the  terraces  of  the  Santa  Toma  are  particularly  significant  because  the 
whole  course  of  the  river  lies  in  a  region  of  abundant  vegetation.  This  suggests  that  in 
tropical  regions,  unlike  those  of  the  temperate  zone,  changes  of  climate  have  appreciably 
influenced  the  amount  of  vegetation,  or  at  least  the  rate  of  erosion,  not  only  in  aiid  regions 
but  even  where  dense  forests  prevail. 

If  the  terraces  are  really  of  chmatic  origin  important  consequences  follow  when  we 
investigate  their  relation  to  ruins.  Among  the  greatest  of  the  ruins  of  Maya  land  are 
those  of  Copan  on  the  Copan  tributary  of  the  Motagua,  just  over  the  Guatemalan  border 
in  northern  Honduras.  Beginning  at  the  wretched  little  modern  village  of  Copan,  the  ruins 
extend  up  the  right  bank  of  the  river  for  at  least  1.5  miles,  and  in  the  last  three-quarters  of 
a  mile  of  that  distance  the  ancient  walls  are  practically  continuous.  At  the  southwestern 
end  of  the  main  ruins  the  walls  of  the  chief  citadel,  or  temple,  rise  directly  from  the  river, 
which  is  almost  undermining  them  and  may  soon  cause  their  fall.  The  relation  of  the  wall 
to  the  deposits  of  the  river  is  shown  in  the  profile  and  cross-section  of  figure  73,  and  in  the 
accompanying  description.  It  is  also  illustrated  in  Plate  10,  b,  page  211. 

Before  the  full  meaning  of  the  diagram  is  explained,  attention  should  be  called  to 
figure  74.  From  this  it  will  be  seen  that  the  ruins  stand  upon  a  terrace  about  18  feet  above 
the  present  low-water  level.  They  follow  this  very  closely  and  were  evidently  built  along  it. 
Just  below  it  there  lies  another  terrace,  12  feet  above  low-water  level,  and  to-day  quite 
as  good  a  place  for  houses  as  is  the  upper  terrace.  The  fact  that  no  trace  of  ruins  is  found 
upon  it  and  the  conditions  of  deposition  shown  in  figure  73  seem  to  indicate  that  when 


214 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Copan  was  an  inhabited  city  the  edge  of  the  18-foot  terrace  was  washed  by  the  river. 
To-day  floods  sometimes  reach  the  foot  of  the  12-foot  terrace,  but  never  rise  higher.  If 
the  river  should  again  proceed  to  deepen  its  channel  the  present  flood-plain  would  in  turn 

KEY  TO  FIGURE  73, 

1.  =  Original  river  deposits  on  which  the  ancient  town  of  Copan  was  built 
Upper  parts  with  some  clay  and  fine  gravel,  but  mostly  coarse  cobbles 
with  small  bands  of  finer  gravel.  The  upper  cobble  layers  are  in  a 
matrix  of  more  clayey  material  and  look  as  if  they  had  been  laid  down 
to  a  depth  of  5  to  6  feet,  under  somewhat  unusual  conditions,  e.  g.,  as 
if  the  ordinary  course  of  the  river  had  been  interfered  with  by  man. 
The  top  of  this  deposit  is  about  18  to  19  feet  above  present  low-water 
level,  and  11  to  12  feet  above  present  high-water  level. 

2.  =  Masonry  wall  extending  down  6  to  7  feet  below  top  of  (1),  apparently 
to  low-water  level  of  the  period  when  it  was  built.  Otherwise  the 
wall  must  have  been  laid  in  a  trench,  which  is  improbable  because  of 
the  even  stratification  of  (4). 

3.  =  Rubble  filling,  placed  inside  of  wall  to  form  the  great  mound  on  which 
the  temple  is  built. 

4.  =  Fine  alluvial  materials  such  as  fine  water-laid  gravel  and  sand  mixed 
with  some  layers  of  rounded  cobbles  and  also  with  layers  containing 
angular  bits  of  limestone,  broken  cherty  flint,  and  also  larger  blocks  of 
the  limestone  of  which  the  walls  are  made.  This  looks  like  a  deposit 
laid  down  in  water  just  after  the  wall  was  built.  It  lies  outside  of  (2) , 
just  as  (2)  lies  outside  of  (1)  and  (3),  and  it  lies  on  (1)  and  seems  to 
coalesce  with  it.  Its  top  is  about  4  feet  below  that  of  (1).  The  relative 
ages  of  (3)  and  (4)  are  not  evident. 

5.  =  Broken  rubble  from  the  ruins  up  above.  It  lies  outside  of  (2)  and 
above  (4).  It  is  like  (3),  only  more  irregular  and  with  lees  cobble¬ 
stones,  probably  because  it  fell  from  the  high  parts  of  the  wall. 

6.  =  About  10  feet  of  even  layers  of  cobbles  laid  down  by  man  in  a  reddish 
clayey  matrix.  No  significance. 

7.  =  Grayish  rubble.  No  significance. 

become  a  third  terrace,  but  there  seems  to  be  no  such  tendency.  It  should  be  added  that 
above  the  18-foot  terrace  are  traces  of  others  of  much  greater  age,  but  these  do  not  con¬ 
cern  us. 

The  facts  which  have  just  been  stated,  and  which  are  illustrated  in  figures  73  and  74, 
seem  to  indicate  that  the  history  of  the  Copan  River  in  relation  to  the  ruins  has  been  approxi¬ 
mately  as  follows:  The  earhest  of  the  finely  carved  stelae  at  Copan  bears  a  date  which 
Morley  reads  as  251  a.d.,  but  which  Bowditch  puts  about  250  years  earlier.  The 
lowest  walls  of  the  main  temple  or  citadel  must  quite  surely  have  been  built  before  the 
stelae  were  carved,  and  it  seems  safe  to  say  that  they  probably  date  back  before  the  time 
of  Christ.  Previous  to  that  date  the  river  had  built  up  its  flood-plain  approximately  to 
the  present  18-foot  level.  At  that  time,  however,  it  probably  was  not  aggrading  its  flood¬ 
plain  to  any  great  extent,  for  in  that  case  the  town  would  frequently  have  been  flooded. 
Nevertheless,  it  may  sometimes  have  overflowed  into  the  town,  and  to  this  may  be  due 
the  somewhat  disturbed  stratification  of  the  upper  part  of  deposit  No.  1  in  figure  73,  a 
deposit  which  lies  inside  the  wall  and  corre¬ 
sponds  with  the  general  upper  layer  of  the  18- 
foot  terrace.  Even  if  this  is  not  the  case,  the 
river  rose  quite  high,  for  on  the  outside  of  the 
wall  it  deposited  materials  (No.  4  in  figure  73) 
within  4  feet  of  the  level  of  the  main  terrace. 

Next  the  river  cut  down  its  channel  to  an  un¬ 
known  depth  below  the  18-foot  terrace.  Then 
it  built  up  its  flood-plain,  perhaps  much,  per¬ 
haps  very  little,  and  formed  the  present  12-foot 
level.  Next  it  again  cut  downward,  and  then  once  more  laid  down  deposits  to  form  the 
present  flood-plain. 

How  markedly  the  processes  of  degradation  and  aggradation  were  separated  we  have 
as  yet  no  knowledge,  but  on  the  upper  Motagua  and  in  most  of  the  other  parts  of  the  world 
where  such  terraces  are  seen  the  separation  is  usually  distinct.  If  we  assume  that  the  same  is 


Fig.  74. — Relation  of  Terraces  and  Ruins  at  Copan. 

Numerals  indicate  approximate  height  above  low-water 
level.  R  =  River.  C  —  Ruined  walls  of  Copan. 


Fig.  73. — Diagrammatic  Sections  of  Wall  and 
Deposits  at  Copan  Ruins. 

A.  Oblique  section  as  seen  from  river. 

B.  Cross-section  along  M-N. 


GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION. 


215 


true  here,  and  if  we  further  assume  the  correctness  of  our  previous  conclusions  as  to  the 
synchronism  of  wet  times  in  California  and  dry  times  in  Central  America,  we  may  frame 
the  following  tentative  table  on  the  basis  of  the  curve  of  growth  of  the  sequoias: 

(1)  Previous  to  100  b.c.  Period  of  aggradation  and  presumably  of  increasing  aridity  antecedent  to  the  building 

of  Copan. 

(2)  100  B.C.-250  A.D.  Period  of  high  river-level,  but  not  of  much  change  of  level  in  flood-plain,  that  is,  a  time 

when,  although  aridity  was  no  longer  increasing,  there  was  no  special  tendency  toward  more  moisture. 

Building  of  Copan. 

(3)  250-700  A.D.  Period  of  degradation  or  downcutting  by  the  river  up  to  the  edge  of  the  18-foot  terrace— that  is, 

a  time  when  the  amount  of  rain  and  of  vegetation  was  increasing.  Occupation  of  Copan  followed  by 

decline  and  abandonment.  The  date  of  the  last  monument  is  about  500  a.d.  according  to  Spinden  and 

230  A.D.  according  to  Bowditch. 

(4)  700-1000  A.D.  Period  of  aggradation  and  of  increasing  aridity  during  which  the  river  built  up  its  flood-plain  to 

the  12-foot  level. 

(5)  1000-1300  A.D.  Period  of  degradation  and  of  increasing  moisture  with  deepening  of  river  channel  in  such  a 

way  as  to  form  the  12-foot  terrace. 

(6)  1300-1900  A.D.  Period  of  minor  fluctuations  of  climate  with  alternate  deposition  and  erosion,  the  present  flood- 

plain  being  approximately  the  mean  level. 

In  a  table  such  as  this  the  possibility  of  error  is  great,  for  the  number  of  unknown 
factors  is  large  and  many  assumptions  must  of  necessity  be  made.  I  do  not  present  it  as 
in  any  way  final,  or  as  more  than  a  mere  suggestion  of  the  way  in  which,  when  far  fuller 
information  is  available,  we  may  perhaps  be  able  to  correlate  such  diverse  phenomena  as 
changes  of  climate,  variations  in  the  activity  of  rivers,  and  events  of  history.  Its  present 
importance  lies  in  the  fact  that  when  we  submit  our  climatic  theories  to  the  severe  test  of 
a  comparison  between  the  growth  of  trees  in  California  and  the  activity  of  rivers  in  Guate¬ 
mala,  we  at  least  find  no  obvious  contradiction. 

Leaving,  now,  this  rather  speculative  matter,  we  may  briefly  sum  up  the  evidence  of 
the  terraces.  Two  points  stand  out  clearly: 

(1)  There  can  be  no  question  that  in  Guatemala  we  find  terraces  of  the  kind  that  our 
climatic  theory  would  lead  us  to  expect.  The  only  surprising  thing  is  that  they  occur  in 
places  where  the  vegetation  is  denser  than  we  should  have  anticipated,  which  suggests  that 
if  climatic  changes  have  occurred,  they  have  affected  vegetation  in  moist  tropical  regions 
more  than  in  moist  temperate  regions. 

(2)  The  terrace-making  process  has  been  active  since  the  foundation  of  Copan,  one  of 
the  chief  of  the  ancient  Maya  towns,  but  the  activity  has  been  mild  compared  with  that  of 
earlier  times.  If  the  tectonic  theory  of  alluvial  terraces  is  correct,  these  two  points  have 
no  special  significance.  If  the  climatic  theory  is  correct,  they  add  much  to  the  reliability 
of  our  main  conclusions. 

We  come  now  to  a  subject  much  more  significant  than  the  terraces.  In  Guatemala  the 
former  distribution  of  population  and  still  more  of  culture  was  utterly  different  from  that 
of  to-day.  Almost  nowhere  else  in  the  whole  world  have  2,000  years  or  less  produced  so 
profound  a  change  as  in  this  little  country  of  only  about  48,000  square  miles.  The  normal 
decay  of  races,  the  interplay  of  historic  forces,  the  invasion  of  barbarians,  the  decadence 
due  to  luxury,  vice,  and  irrehgion,  the  change  of  the  center  of  world  power,  each  or  all  of 
these  causes,  or  any  others  usually  appealed  to  by  historians,  can  not  explain  the  matter. 
The  question  is  not  why  the  Maya  civilization  arose,  nor  why  it  fell.  We  may  assume 
that  it  arose  because  it  is  the  nature  of  a  young  and  vigorous  race  to  make  progress,  and 
that  it  fell  because  it  is  the  nature  of  an  old  and  exhausted  civilization  to  decay.  The 
assumption  does  not  help  us  in  the  least,  for  it  does  not  touch  our  problem.  To-day  the 
most  progressive  and  energetic  people  of  Guatemala,  its  densest  population,  its  greatest 
towns,  its  center  of  wealth,  learning,  and  culture,  so  far  as  these  things  exist,  are  all  located 
in  the  relatively  open,  healthful,  easily  accessible  and  easily  tillable  highlands;  in  the  past 
these  same  things  were  located  in  the  most  inaccessible,  unhealthful,  and  untillable  low 
lands.  Why  the  change? 


216 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


From  the  point  of  view  of  present  habitability  Guatemala,  together  with  British 
Honduras,  is  divided  into  three  main  belts  dependent  on  vegetation — the  Atlantic  forest, 
the  central  dry  land,  and  the  Pacific  forest.  Each  of  these  in  turn  may  be  divided  into 
two  parts.  The  plain  of  British  Honduras  in  the  north  to  a  width  of  50  miles,  and  the 
mountains  of  the  southern  part  of  that  country  and  of  eastern  Guatemala  to  a  distance  of 
perhaps  30  miles  from  the  coast  form  the  first  division  of  the  Atlantic  forest.  Showers  at 
all  seasons,  either  from  the  trade  winds  in  winter  or  from  the  subequatorial  area  of  low 
pressure  in  summer,  cause  the  land  to  be  covered  with  a  dense  tropical  forest  and  to  be 
infested  with  malignant  types  of  malarial  fevers.  Only  on  the  coast  are  there  any  real 
towns,  and  they  exist  chiefly  by  grace  of  the  trade  winds,  which  blow  freshly  from  the 
ocean  and  drive  away  the  mosquitoes.  Strung  along  the  beach,  under  the  cocoanut  palms, 
the  low  whitewashed  houses  of  these  towns  make  quite  a  show  from  the  sea,  but  back  of 
the  first  row  there  is  often  nothing  but  deadly  swamp  and  mosquitoes.  In  the  interior  a 
few  httle  villages  sit  in  clearings  by  the  brink  of  the  somber  rivers,  and  wait  in  sun  or  rain 
for  precious  mahogany  logs  to  be  hauled  or  floated  out  of  the  interior.  Save  for  these  few 
people  no  one  inhabits  the  dense  forests.  If  the  coast  towns  and  the  mahogany-cutters  be 
excluded,  the  whole  region  can  not  boast  a  population  of  much  more  than  one  person  to 
every  10  square  miles,  while  even  if  the  towns  and  w'oodcutters  be  included,  British  Hon¬ 
duras  with  an  area  of  7,500  square  miles  has  only  42,000  people,  or  less  than  6  to  the  square 
mile.  The  forests  and  fevers  now  keep  mankind  away,  and  apparently  much  the  same 
was  true  in  the  past,  for  we  find  here  only  a  few  widely  scattered  ruins. 

Inland  from  the  coast  strip  there  lies  another  section  of  the  Atlantic  forest,  occupying 
most  of  the  almost  unexplored  and  semi-independent  Guatemalan  province  of  Peten,  and 
extending  south  past  Quirigua  towards  Copan.  In  the  north  this  Peten  strip  is  a  plain 
from  which  rise  a  few  low  ridges  running  east  and  west  and  having  a  height  of  1,000  feet 
more  or  less.  In  the  south  it  becomes  mountainous.  The  vegetation  is  almost  as  dense  as 
that  of  the  coast  strip,  except  that  in  Peten  considerable  areas  of  grassy  savanna  prevail, 
thin  pine  forests  grow  in  the  sandy  tracts  known  as  “pine  ridges,”  and  on  the  westward 
edge  and  in  other  favored  spots — among  which  Flores  on  Lake  Peten  is  the  chief — the 
forest  breaks  down  into  jungle.  The  savannas,  as  already  suggested,  are  due  either  to  an 
excess  of  water,  often  held  near  the  surface  by  clayey  hardpan,  or  to  sand.  The  pine 
ridges,  which  are  not  ridges  but  merely  slight  swellings  in  the  plain,  are  due  to  accumulations 
of  sand.  Neither  in  the  past  nor  at  present  does  it  ever  appear  to  have  been  possible  to 
cultivate  either  the  savannas  or  the  pine  ridges,  but  since  the  introduction  of  cattle  by  the 
Spaniards,  they  have  been  utilized  somewhat  for  pasturage.  They  possess  not  only  the 
advantage  of  being  fit  for  cattle-raising,  but  of  being  relatively  healthful,  and  of  being 
bordered  by  narrow  strips  of  jungle  wherein  primitive  agriculture  is  possible.  In  the 
more  extensive  jungle  regions  on  the  borders  of  the  Peten  strip  a  few  villages  are  located, 
among  which  Copan  is  most  worthy  of  mention.  Aside  from  the  limited  areas  of  savannas, 
pine  ridges,  and  jungle,  the  country  is  covered  with  forest,  and  is  so  feverish  and  so  difficult 
to  cultivate  that  its  only  inhabitants  are  mahogany-cutters,  gatherers  of  chicle  gum,  or 
raisers  of  bananas  for  export.  All  of  these  occupations,  together  with  cattle-raising,  are 
due  entirely  to  the  influence  of  modern  European  civilization,  and  had  no  place  in  the  pre- 
Columbian  period.  The  banana  plantations  have  grown  up  within  a  few  years  and  are 
practically  all  the  work  of  the  United  Fruit  Company,  which  employs  over  4,000  people 
in  the  valley  of  the  Motagua  River.  Only  some  powerful  stimulus,  Uke  the  demand  of  the 
United  States  for  fruit,  could  cause  such  plantations  to  arise;  the  strictest  supervision  is 
necessary  in  order  that  the  bushes  may  be  cut  every  three  months,  for  in  a  year  the  native 
vegetation  grows  10  feet  or  so,  and  if  left  to  itself  would  soon  choke  the  banana  plants. 
Still  more  unremitting  vigilance  is  necessary  to  keep  both  the  white  men  and  the  natives 
in  health.  From  the  wages  of  every  employee,  whether  he  receive  50  cents  or  50  dollars 


GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION. 


217 


per  day,  the  company  takes  2  per  cent  to  pay  for  sanitary  measures.  Every  plantation 
has  its  doctor  and  dispensary,  and  natives  and  foreigners  alike  are  continually  dosed  with 
quinine.  Yet  even  so,  at  certain  seasons  of  the  year,  a  single  train  may  carry  a  score  of 
staggering  fever  patients.  The  present  hospitals  are  wholly  inadequate,  and  in  1913  the 
company  was  erecting  a  new  hospital  at  a  cost  of  $125,000.  Mr.  Victor  M.  Cutter,  manager 
of  the  Guatemala  division  of  the  United  Fruit  Company,  states  that  in  his  district  about 
90  per  cent  of  the  people,  including  both  natives  and  whites,  suffer  from  malaria  and  its 
sequelae.  He  thinks  that  approximately  20  per  cent  have  malaria  in  a  serious  form  in 
spite  of  preventive  measm’es. 

In  the  entire  Peten  strip  of  the  Atlantic  forest,  from  Copan  on  the  south  up  through 
Quirigua,  the  lake  of  Izabal,  and  the  province  of  Peten,  it  is  probable  that  the  total  popu¬ 
lation  does  not  exceed  20,000  in  an  area  of  nearly  15,000  square  miles.  If  the  cattle-raisers, 
mahogany-cutters,  gum-gatherers,  and  banana-raisers  be  excluded,  and  if  we  include  only 
the  people  who  procure  a  living  in  ways  possible  before  the  coming  of  the  white  man,  the 
population  is  reduced  to  probably  less  than  10  per  cent  of  the  figures  given,  or  only  1  person 
for  7  square  miles.  Of  course  these  figures  are  mere  approximation;  there  is  no  such  thing 
as  a  census,  for  much  of  the  country  is  still  unexplored  and  the  wild  Indian  tribes  practically 
ignore  the  Guatemalan  supremacy.  Yet  day  after  day  the  traveler  finds  no  inhabitants, 
and  places  which  appear  on  the  map  as  villages  prove  to  have  only  two  or  three  houses  or 
merely  an  abandoned  hut.  Roads  and  even  trails  are  almost  non-existent,  and  in  most 
places  the  machete  must  constantly  be  used  to  open  up  a  pathway.  Mr.  Frank  Blance- 
neaux,  who  for  6  or  7  years  spent  a  large  part  of  his  time  in  traveling  through  Peten  in 
search  of  mahogany,  probably  knows  that  province  as  thoroughly  as  any  one.  He  thinks 
that  the  population  does  not  exceed  10,000,  and  that  at  least  95  per  cent  of  it  consists  of 
cattle-raisers,  mahogany-cutters,  and  gum-gatherers.  Nowhere  has  he  seen  a  village  of 
more  than  a  hut  or  two  in  the  genuine  forest,  and  nowhere  do  people  practise  any  real 
agriculture  in  the  forest  as  opposed  to  the  jungle.  South  of  Peten,  along  the  line  of  the 
railway  from  Puerto  Barrios  to  Guatemala,  for  60  miles  from  the  Atlantic  coast,  until  one 
comes  to  the  poor  little  village  of  Los  Amates,  there  would  not  be  a  single  inhabited  place 
were  it  not  for  the  banana  plantations  of  the  United  Fruit  Company.  Los  Amates  itself 
lies  on  the  edge  of  the  forest,  where  it  breaks  down  into  big  jungle. 

Whatever  may  be  the  exact  figures  as  to  population,  it  is  evident  that  heavy  rains, 
dense  vegetation,  and  malignant  fevers  to-day  render  the  Peten  strip  of  the  Atlantic  forest 
almost  uninhabitable;  yet  in  the  past  this  was  by  no  means  the  case.  Practically  all  of 
the  great  Maya  ruins  outside  of  Yucatan  lie  in  this  strip  or  in  its  northern  and  northwestern 
continuation  in  the  Mexican  provinces  of  Chiapas,  Tabasco,  and  Campeche.  Copan,  one 
of  the  most  remarkable  of  the  ancient  cities,  lies  on  its  edge,  although  not  actually  in  it; 
Quirigua  lies  within  it,  although  only  a  few  miles  from  the  border;  and  Seibal,  Tikal, 
Naranjo,  and  a  score  of  others  as  far  as  Palenque  in  the  north,  lie  well  within  its  dense 
jungle  and  forests.  These  places  were  obviously  towns  of  importance,  such  as  grow  up 
in  interior  agricultural  districts  far  from  important  lines  of  communication  only  when 
there  is  a  considerable  population  round  about.  How  dense  the  former  population  may 
have  been  we  can  not  estimate,  for  the  cover  of  vegetation  is  so  thick  that  we  have  no  idea 
of  the  exact  number  of  ruins;  but  it  is  scarcely  an  exaggeration  to  say  that  for  every  family 
now  supported  by  ordinary  agriculture  there  was  probably  a  town  or  village  in  the  days  of 
the  Mayas. 

Turning  now  to  the  relatively  dry  portion  of  Guatemala,  the  second  of  our  three  divi¬ 
sions,  we  find  it  divided  into  arid  bush  country,  lying  in  low,  isolated  valleys  or  basins, 
such  as  Zacapa,  and  highlands  where  pine  or  temperate  forests  prevail.  The  bush  country 
is  unimportant,  being  of  small  area.  In  some  places  it  is  so  hot  and  dry  that  cacti  and 
mesquite  bushes  make  it  look  Hke  the  lowlands  of  Arizona.  It  is  fairly  well  inhabited  and 


218 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


moderately  healthful.  The  people  are  in  advance  of  the  poor  denizens  of  the  forest  zone, 
but  are  miserably  inefficient,  idle,  weak-willed,  and  immoral.  The  real  strength  of  Guate¬ 
mala  is  in  the  highlands,  where  the  vegetation  takes  on  an  aspect  suggestive  of  the  temperate 
zone.  There,  on  the  plateau  amid  pine-clad  hills,  all  the  large  towns  are  now  located. 
The  conditions  of  health,  from  a  tropical  point  of  view,  are  everywhere  good.  Typhus, 
dysentery,  and  other  disorders,  to  be  sure,  often  sweep  the  country;  and  faces  pitted  by 
small-pox  are  frequently  seen.  These  diseases,  however,  although  causing  a  high  death- 
rate,  are  temporary.  Their  ravages  are  as  nothing  compared  with  those  of  the  deadly 
malarial  fevers  which  in  the  lowland  forests  return  season  after  season  to  blight  and  destroy 
the  same  places  and  the  same  people. 

From  the  coast  upward,  according  to  universal  testimony,  the  health,  energy,  industry, 
and  thrift  of  the  native  Guatemalans  in  general  show  an  increase.  It  seems  a  curious 
reversal  of  what  we  are  wont  to  call  normal  conditions,  when  one  sees  rich,  fertile  plains 
along  the  coast  almost  uninhabited,  then  finds  the  population  fairly  dense  on  steeply 
sloping,  stony  mountain-sides  at  altitudes  of  3,000  to  5,000  feet,  and  finally  on  the  hilly 
plateau  (at  8,000  feet)  sees  little  thatched  houses  clustering  thickly  ever3nvhere,  and  every 
available  bit  of  land  almost  as  carefully  and  industriously  cultivated  as  in  China.  Even 
more  curious,  perhaps,  is  the  fact  that  here,  where  the  population  is  now  so  dense,  there  are 
relatively  few  important  ruins  and  none  of  the  advanced  type  found  in  Peten.  There  is 
no  reason  to  think  that  ruins  which  once  existed  have  disappeared  to  any  greater  extent 
than  has  happened  in  Egypt,  Syria,  Greece,  Rome,  or  any  other  country  where  a  high  civili¬ 
zation  in  the  past  has  been  followed  by  a  dense  population  at  present. 

Moreover,  ruins  of  a  certain  kind  are  found  in  considerable  numbers,  but  they  are 
insignificant  and  probably  of  late  date  compared  with  those  of  Peten.  The  carved  stones 
which  one  sees,  for  example,  at  Guarda  Viejo,  near  Guatemala  City,  are  relatively  small, 
crudely  executed,  and  inartistic,  utterly  different  from  the  clean-cut,  highly  complex,  and 
truly  artistic  stelae  of  enormous  size  at  Quirigua.  The  plain,  almost  unadorned  structures 
at  Quiche,  the  greatest  ruins  on  the  plateau,  bear  to  the  highly  developed  groups  of  buildings 
and  monuments  at  Copan  about  the  same  relation  that  modern  Guatemalan  churches  bear 
to  St.  Peter’s  at  Rome.  (See  Plate  10,  page  211;  Plate  11,  page  218;  and  Plate  12,  page 
230.)  In  the  days  of  the  Mayas  the  highlands  may  have  been  as  densely  populated  as 
to-day,  although  we  have  no  positive  proof  of  this,  but  instead  of  being  the  center  of  the 
life  and  activity  of  the  country  they  were  a  provincial  outpost. 

Beyond  the  highlands,  our  third  division  (the  Pacific  forest)  resembles  the  Atlantic 
forest  in  certain  ways,  but  with  interesting  points  of  difference.  As  already  explained, 
the  lower  slopes  of  the  mountains  and  the  inner  edge  of  the  piedmont  plain  (from  an  altitude 
of  about  500  to  4,000  feet)  are  covered  with  dense  vegetation.  At  an  altitude  of  approxi¬ 
mately  2,000  to  3,000  feet  the  vegetation  attains  the  dignity  of  real  tropical  forest  with 
mahogany  trees,  tree  ferns,  and  the  like,  while  on  either  side  it  assumes  the  form  of  forest¬ 
like  jungle  merging  gradually  into  pine  forest  toward  the  uplands  and  into  jungle  and  bush 
toward  the  coast.  All  except  the  upper  mountainous  part  of  the  region  is  malarial  and 
unhealthful,  although  not  so  bad  as  the  Atlantic  forest  because  the  drainage  is  better. 
The  strip  of  real  forest  would  to-day  be  practically  uninhabited  were  it  not  that  the  demands 
of  the  modern  civilized  world  have  led  to  the  cultivation  of  coffee,  chiefly  by  German 
companies  with  Indian  labor  brought  from  the  highlands.  Lower  down,  on  the  edge  of 
the  plain,  there  would  be  a  small  population  even  without  the  impetus  of  coffee.  A  few 
little  towns  like  Retalhuleu,  Santa  Lucia,  and  Escuintla  date  back  many  centuries.  They 
are  notoriously  unhealthful,  however;  their  inhabitants  are  universally  pronounced  in¬ 
efficient  and  apathetic;  and  their  population  of  2,000  to  12,000  people  is  only  10  to  20  per 
cent  as  large  as  that  of  corresponding  towns  on  the  plateau.  Yet  here,  curiously  enough, 
we  again  find  abundant  traces  of  an  ancient  race  of  relatively  high  culture.  The  ruins  are 


HUNTINGTON 


PLATE  11 


The  ruins  of  Quiche,  ihe  most  extensive  on  the  Guatemalan  plateau  The  steep  ^ope  in 

shows  how  the  volcanic  tuff  is  dissected  by  precipitous  canyons.  It  also  illustrate  Y  Y 

avJabt  rrea  is  uS  "  ‘^e  construction  of  very  narrow 

NelTvTew  of  the  most  imposing  ruins  of  Quiche  The  absence  of  good  stonework  in  spite  of  the  recent 

age  of  the  ruins  illustrates  their  inferiority  to  those  of  Copan  and  t^uirigua. 


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GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION. 


219 


by  no  means  equal  to  those  of  the  Peten  strip,  and  there  appear  to  be  few  hieroglyphics  j 
nevertheless,  they  belong  to  the  same  civilization,  although  to  a  later  stage  subject  to 
foreign  (Nahua)  influence.  At  places  like  Paul  and  Pantaleon  great  blocks  of  hard  basalt 
have  been  found  carved  with  scenes  of  sacrifice  or  chiseled  to  represent  gigantic  faces 
whose  peculiar  types  of  slit  nostril,  high  cheek,  or  projecting  mouth  can  still  be  recognized 
in  individual  Indians.  (See  Plates  9,  c,  page  189,  and  12,  b,  page  230.) 

The  seaward  portion  of  the  Pacific  belt  needs  little  further  comment.  Beginning  with 
jungle,  where  the  modern  towns  and  ancient  ruins  come  to  an  end,  its  shoreward  portion 
is  covered  with  dense,  low  bushes,  among  which  short  bamboos  are  often  conspicuous. 
Although  dry  and  parched  in  the  winter  season,  much  of  it  becomes  a  vast  swamp  when 
the  rains  swell  the  mountain  streams  and  cause  them  to  spread  out  over  its  flat  expanses. 
Fevers  then  prevail  and  are  often  of  the  “pernicious”  type,  accompanied  by  hemorrhages 
of  blood  producing  immediate  death.  Practically  the  only  inhabitants  are  a  few  cattle- 
raisers,  who  are  described  as  the  lowest  of  the  low.  In  the  past,  conditions  were  apparently 
no  better,  for  we  find  no  trace  of  ruins  here. 

Before  we  consider  the  possible  causes  of  the  contrast  between  the  past  and  present, 
it  will  perhaps  add  to  the  clarity  of  our  ideas  if  our  six  belts  are  arranged  in  tabular  form. 


Table  11. 


Locality. 

Nature  of 
vegetation. 

Health 

conditions. 

Condition  of 
agriculture. 

Present  density 
of  population. 

Condition  of 
population. 

Abundance  and  condition 
of  ruins. 

1.  Atlantic  coast 

Dense  forest . 

Very  unhealthful 

Very  diflScult  . 

Very  scanty .  . 

Degraded . 

Very  few  so  far  as  known,  but 
of  fairly  high  tjT)e. 

2.  Peten  belt . .  . 

Dense  forest  with 
some  savannas 
and  jungle. 

Very  unhealthful 

Very  difficult . 

Very  scanty  .  . 

Degraded . 

Numerous  and  indicating  the 
highest  native  American 
culture. 

3.  Dry  valleys.. 

Bush  or  low  jungle. 

Fairly  healthful . 

Fairly  easy.  .  . 

Moderately 

dense. 

Low,  but  well 
ahead  of  1,  2, 
and  6. 

Moderately  numerous  and  of 
fairly  high  type. 

4.  Highlands . . . 

Pine  forest . 

Healthful . 

Easy . 

V® V  dense .  .  . 

By  far  the  best  in 
Guatemala. 

Quite  numerous,  but  mostly 
of  rather  low  type,  that  is, 
provincial  or  degenerate. 

5.  Pacific  coffee 
belt. 

Forest  and  jungle . 

Unhealthful .... 

Fairly  difficult 

Rather  scanty. 

Low,  but  ahead  of 

1,  2,  and  (i. 

Moderately  numerous  and  of 
fairly  high  type. 

6.  Pacific  coast 

Bush . 

Very  unhealthful 

Difficult . 

Very  scanty .  . 

Degraded . 

None  so  far  as  known. 

It  is  worth  while  to  emphasize  the  strange  contrast  between  past  and  present.  The 
belts  along  the  Atlantic  and  Pacific  coasts  may  be  left  out  of  account,  since  in  the  past, 
as  at  present,  they  appear  to  have  been  too  forested  and  too  feverish  for  human  occupation 
to  any  great  extent.  To-day  the  other  four  divisions  stand  in  the  following  order  so  far  as 
progress,  achievement,  and  density  of  population  are  concerned:  first,  the  highlands;  second, 
the  dry  valleys;  third,  the  coffee  belt;  fourth,  the  Peten  strip.  In  the  past  the  ruins  tell  a 
very  different  tale:  the  Peten  strip  stood  first,  then  the  coffee  belt  and  the  dry  valleys, 
and  last  of  all  the  highlands,  the  reverse  of  the  present  order.  To-day,  in  Central  America, 
the  physical  conditions  under  which  mankind  tends  most  to  increase  in  numbers  and  to 
progress  in  culture  appear  to  be  high  altitude,  good  drainage,  and  a  fairly  long  dry  season. 
Altitude  in  itself,  however,  does  not  appear  to  be  essential,  for  northern  Yucatan  seems  as 
well  off  as  the  highlands  of  Guatemala.  Perhaps  the  exposure  of  that  part  of  Yucatan  to 
the  ocean  and  to  strong  winds  from  the  north  produces  the  same  effect  as  elevation.  Op¬ 
posed  to  these  favorable  conditions  stand  those  which  conspire  to  hold  man  back  and  keep 
him  in  a  low  stage  of  civilization.  Omitting  low  altitude,  which  is  important  merely  because 
of  its  effect  on  other  factors,  we  are  confronted  by  four  chief  conditions :  first,  the  prevalence 
of  fevers;  second,  the  prevalence  of  great  heat  and  moisture  almost  without  change  from 
season  to  season;  third,  the  difficulty  of  carrying  on  permanent,  intensive  agriculture; 
and  fourth,  the  relative  ease  of  getting  a  living  in  the  jungle. 

Little  by  little  the  world  is  learning  that  the  most  dangerous  diseases  are  not  necessarily 
those  which  show  the  highest  death-rate.  The  plagues  of  the  Middle  Ages  loom  large  in 


220 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


history,  but  they  did  not  do  a  tithe  as  much  harm  as  syphilis  has  done.  Yellow  and  typhus 
fevers  may  decimate  a  population,  but  they  are  far  preferable  to  the  slow,  irresistible 
ravages  of  recurrent  malarial  fevers,  which  rarely  seem  to  kill,  but  merely  undermine  the 
constitution,  leaving  both  mind  and  body  inefficient.  Tuberculosis,  in  our  own  land, 
is  so  dreaded  that  we  wage  a  crusade  against  it,  but  its  dangers  are  probably  far  less  than 
those  of  the  insidious  colds  which  year  after  year  attack  fully  half  of  our  northern  popu¬ 
lations,  not  killing  them,  not  even  doing  more  than  lessen  their  efficiency  for  a  few  days, 
and  yet  in  the  aggregate  causing  an  incalculable  amount  of  damage  and  giving  an  opening  for 
a  large  part  of  our  cases  of  consumption,  diphtheria,  deafness,  and  many  other  affiictions. 
Just  as  in  our  huge  folly  we  long  neglected  consumption,  and  still  largely  neglect  the  even 
more  insidious  ordinary  colds,  so  the  man  within  the  tropics  often  ignores  malaria.  Again 
and  again  I  have  talked  with  people  who  said  there  was  no  fever  in  the  particular  place  where 
they  lived  or  that  they  had  not  had  fever,  but  before  the  next  meal  they  took  a  dose  of 
quinine,  and  that  same  night,  perhaps,  they  reeled  with  a  touch  of  fever  or  shivered  with  a 
chill.  They  called  it  “nothing,”  but  even  quinine  did  not  prevent  them  from  being  weak¬ 
ened  by  it.  Few  foreigners,  especially  children,  can  live  long  in  the  lowlands  under  ordinary 
conditions  without  being  affected.  As  for  the  natives,  it  is  often  stated  that  they  become 
immune  to  fevers,  but  here  is  what  Sir  Ronald  Ross,  of  the  Liverpool  School  of  Tropical 
Medicine,  and  one  of  the  chief  authorities  on  the  subject,  has  to  say: 

“These  diseases  do  not  affect  only  immigrant  Europeans;  they  are  almost  equally  disastrous 
to  the  natives,  and  tend  to  keep  down  their  numbers  to  such  a  low  figure  that  the  survivors  can 
subsist  only  in  a  barbaric  state.  To  believe  this  one  has  to  see  a  village  in  Africa  or  India  full  of 
malaria,  kala-azar,  or  sleeping  sickness,  or  a  town  under  the  pestilence  of  cholera  or  plague. 
Nothing  has  been  more  carefully  studied  of  recent  years  than  the  existence  of  malaria  amongst 
indigenous  populations.  It  often  affects  every  one  of  the  children,  probably  kills  a  large  pro¬ 
portion  of  the  new-born  infants,  and  renders  the  survivors  ill  for  years.  Here  in  Europe  nearly 
all  our  children  suffer  from  certain  diseases — measles,  scarlatina,  and  so  on.  But  these  maladies 
are  short  and  slight  compared  with  the  enduring  infection  of  malaria.  When  I  was  studying 
malaria  in  Greece  in  1906  I  was  struck  with  the  impossibility  of  conceiving  that  the  people  who 
are  now  intensely  inflicted  with  malaria  could  be  like  the  ancient  Greeks  who  did  so  much  for 
the  world;  and  I  therefore  suggested  the  hypothesis  that  malaria  could  only  have  entered  Greece 
at  about  the  time  of  the  great  Persian  wars — a  hypothesis  which  has  been  very  carefully  studied 
by  Mr.  W.  H.  S.  Jones.  One  can  scarcely  imagine  that  the  physically  fine  race  and  the  mag¬ 
nificent  athletes  figured  in  Greek  sculpture  could  ever  have  spent  a  malarious  and  spleno-megalous 
childhood.  And  conversely,  it  is  difficult  to  imagine  that  many  of  the  malarious  natives  in  the 
tropics  will  ever  rise  to  any  great  height  of  civilization  while  that  disease  endures  amongst  them. 
I  am  aware  that  Africa  has  produced  some  magnificent  races,  such  as  those  of  the  Zulus  and  the 
Masai,  but  I  have  heard  that  the  countries  inhabited  by  them  are  not  nearly  so  disease-ridden 
as  many  of  the  larger  tracts.  At  all  events,  whatever  may  be  the  effect  of  a  malarious  childhood 
upon  the  physique  of  adult  life,  its  effects  on  the  mental  development  must  certainly  be  very  bad, 
while  the  disease  always  paralyzes  the  material  prosperity  of  the  country  where  it  exists  in  an 
intense  form. 

“  Consider  now  the  effects  of  yellow  fever,  that  great  disease  of  tropical  America.  The  Liver¬ 
pool  School  sent  four  investigators  to  study  it,  and  all  these  four  were  attacked  within  a  short 
time.  One  died,  one  was  extremely  ill,  and  two  suffered  severely.  The  same  thing  tended  to 
happen  to  all  visitors  in  those  countries.  They  were  almost  certain  of  being  attacked  by  yellow 
fever,  and  the  chances  of  death  were  one  to  four.  But  malaria  and  yellow  fever  are  only  some  of 
the  more  important  tropical  diseases.  Perhaps  the  greatest  enemy  of  all  is  dysentery,  which  in 
the  old  days  massacred  thousands  of  white  men,  and  millions  of  natives  in  India,  America,  and 
all  hot  countries,  and  rendered  survivors  ill  for  years.  Malaria  has  always  been  the  bane  of 
Africa  and  India;  the  Bilharzia  parasite  of  Egypt;  and  we  are  acquainted  with  the  ravages  of 
kala-azar  and  sleeping  sickness.  Apart  from  these  more  general  or  fatal  maladies,  life  tends 
to  be  rendered  unhealthy  by  other  parasites  and  by  innumerable  small  maladies,  such  as  dengue 


GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION.  221 

and  sand-fly  fever,  filariasis,  tropical  skin  diseases,  and  other  maladies,  *  *  *  True,  we  have 
many  maladies  in  Europe,  but  in  order  to  compare  the  two  sets  of  diseases  we  should  compare  the 
death-rates.  Whereas  in  England  it  is  a  long  way  below  20  per  1,000  per  annum,  throughout 
the  tropics  it  is  nearer  40  per  1,000.  In  India  alone  malaria  kills  over  1,000,000  persons  a  year, 
and  dysentery  and  malaria  kill  many  hundreds  of  thousands.  I  have  seen  places  in  which  the 
ordinary  death-rate  remains  at  between  50  and  60  per  1,000;  others  which  were  so  unhealthy  that 
they  were  being  deserted  by  their  inhabitants;  and  others,  lastly,  which  were  simply  uninhabitable. 
What  would  people  say  if  such  a  state  of  things  were  to  exist  in  most  villages  in  England,  Scotland, 
and  Ireland?”* 

On  the  whole,  it  seems  safe  to  say  that  in  tropical  countries  the  density  of  population 
and  the  stage  of  culture  depend  to  a  large  extent  upon  the  amount  and  kind  of  fevers;  yet 
fevers  are  far  from  being  the  whole  story.  Few  who  have  ever  been  in  the  torrid  zone  will 
deny  that  under  prolonged  and  unvarying  conditions  of  heat  and  dampness  both  physical 
and  mental  energy  dechne.  One  is  tempted  to  sit  down  idly  and  rest  and  enjoy  the  warm 
air.  When  it  is  time  for  a  new  piece  of  work  one  tends  to  hesitate  and  to  be  uncertain  as  to 
just  how  to  begin.  Of  course  there  are  exceptions,  and  of  course  a  long  inheritance  of 
activity  in  cooler  regions  will  for  years  largely  overcome  these  tendencies.  Nevertheless, 
of  the  scores  of  northerners,  both  American  and  Europeans,  whom  I  have  questioned  in 
the  torrid  zone  there  was  scarcely  one  who  did  not  say  that  he  worked  less  than  at  home. 
At  first  a  considerable  number  said  that  they  had  as  much  energy  as  at  home,  but  then  they 
added  that  it  was  not  necessary  to  work  so  hard,  and  moreover  that  they  did  not  feel  like 
it.  Much  more  striking  was  the  absolute  unanimity  with  which  they  said  that  when  they 
experienced  a  change  of  climate,  especially  if  they  went  from  lowlands  to  highlands,  or 
still  more  when  they  returned  to  the  north,  they  at  once  felt  an  access  of  energy  which 
lasted  some  time  after  their  return.  To  a  New  Englander  accustomed  to  look  upon  our 
Southern  States  as  having  a  warm,  debihtating  climate,  it  is  interesting  to  hear  people  in 
Guatemala  speak  of  being  stimulated  as  soon  as  they  feel  the  cool  winter  air  of  New  Orleans. 
The  natives  of  the  torrid  zone  are  of  course  so  accustomed  to  the  heat  that  they  enjoy  it  and 
suffer  from  even  a  slight  degree  of  cold,  but  the  very  fact  of  being  accustomed  to  the  heat 
seems  to  carry  with  it  the  necessity  of  working  and  thinking  slowly.  The  universality  with 
which  this  is  recognized  in  Central  America  is  significant.  Again  and  again,  when  one 
asks  about  labor  conditions  in  specific  places,  one  is  told,  “Oh,  yes,  the  people  there  are  all 
right,  but  you  know  it’s  always  hot  down  there  and  they  don’t  work  much.”  All  this, 
I  know,  is  perfectly  familiar,  but  it  deserves  emphasis  because  the  great  ruins  are  practically 
all  in  the  hot  country  where  “they  don’t  work  much.” 

In  addition  to  debilitating  fevers  and  an  enervating  uniformity  of  warm,  moist  atmos¬ 
pheric  conditions,  tropical  countries  suffer  from  peculiar  agricultural  conditions.  As  we 
have  already  seen,  in  the  great  forest,  where  rain  falls  at  all  seasons,  the  making  of  clearings 
is  practically  impossible.  In  the  dense  jungle,  such  as  that  at  an  elevation  of  1,000  to  2,000 
feet  in  the  Pacific  coffee  belt  of  Guatemala,  this  is  usually  but  not  always  possible.  It 
depends  on  the  length  and  character  of  the  dry  season  in  February,  March,  and  April. 
Between  two  and  three  weeks  of  steady  sunshine  are  said  to  suffice  to  prepare  the  cut 
bushes  and  smaller  branches  of  the  trees  for  burning,  but  sometimes  there  is  scarcely  a 
rainless  week  during  the  whole  year.  This  happened  in  1913.  People  who  chanced  to 
do  their  cutting  early  burned  their  fields  and  were  able  to  plant  a  corn  crop,  but  many 
cut  too  late  and  failed.  It  is  easy  to  say  that  everyone  ought  to  cut  and  burn  early,  but 
in  the  first  place  the  lethargy  of  the  torrid  zone  leads  people  to  put  things  off  till  the  last 
moment.  In  the  second  place,  if  the  land  is  burned  over  too  early,  weeds  and  bushes  will 
sprout  and  grow  to  a  height  of  a  foot  or  two  before  it  is  time  to  plant  the  corn.  Hence  a 
second  clearing  will  be  necessary,  and  if  a  second  burning  is  impossible  the  corn  will  be  at  a 
disadvantage. 


*  United  Empire,  February  1913,  pp.  123-124.  Sir  Ronald  Ross:  Medical  Science  and  the  Tropics. 


222 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


This  does  not  end  the  difficulties  of  agriculture  in  the  dense  jungle.  The  first  corn 
crop  from  a  given  clearing  is  usually  very  abundant,  but  the  second,  if  it  follow  immediately 
after  the  first,  is  poor,  so  poor  that  it  is  scarcely  worth  raising.  Perhaps  this  is  because 
the  abundant  vegetation  and  constant  rains  cause  many  important  chemical  ingredients 
to  be  leached  quickly  from  the  soil,  or  perhaps  for  some  other  cause.  At  any  rate  the 
regular  custom  is  to  cultivate  a  given  tract  one  year,  let  the  bushes  grow  four  years,  till 
they  are  perhaps  15  to  20  feet  high,  and  in  the  fifth  year  cut,  burn,  and  plant  again.  Thus 
agriculture  in  the  dense  jungle  is  not  only  precarious,  but  it  is  forced  to  be  extensive  and 
superficial  rather  than  intensive  and  careful;  therefore  it  does  httle  to  stimulate  progress. 
In  the  drier  regions,  whether  high  or  low,  the  soil  is  not  so  quickly  exhausted,  especially  if 
the  absence  of  roots  or  other  conditions  make  it  possible  to  turn  up  new  soil  by  plowing  or 
otherwise.  The  crops  are  by  no  means  so  abundant  as  in  the  wetter  places,  but  the  same 
land  can  be  cultivated  year  after  year  with  only  short  periods  of  rest.  The  cultivator 
must  work  harder  than  in  the  wet  places,  but  his  success  is  less  precarious,  the  efforts  of 
one  year  have  a  direct  bearing  on  succeeding  years,  and  permanent  industry  is  encouraged. 

Still  another  disadvantage  of  the  low,  wet  regions  needs  to  be  briefly  discussed.  It  is 
hard  for  mankind  to  get  a  hving  under  any  circumstances  in  the  genuine  tropical  forest, 
and  he  must  work  at  least  moderatelj’-  for  one  in  the  dry  parts  of  tropical  lands.  In  the 
big  jungle,  however,  game  is  abundant,  wild  fruits  ripen  at  almost  all  seasons,  a  few  banana 
plants  and  palm  trees  will  almost  support  a  family,  and  if  a  corn  crop  is  obtained  at  all, 
the  return  is  large  in  proportion  to  the  labor.  Thus,  so  long  as  the  population  is  not  too 
dense,  life  is  easy  and  there  is  little  stimulus  to  effort.  Under  such  conditions  the  state  of 
human  culture  is  not  likely  to  improve,  for  only  by  a  revolutionary  access  of  skill  and 
industry  would  it  be  possible  to  change  from  the  easy,  hand-to-mouth  fife  of  the  present 
to  the  intensive,  industrious  life  which  seems  to  be  a  necessary  condition  where  civilization 
makes  genuine  progress. 

Thus  far  in  this  chapter  we  have  seen  that  the  distribution  of  population  in  Guatemala 
to-day  is  very  different  from  what  it  was  in  the  past.  We  have  further  seen  that  the  physi¬ 
cal  conditions  which  make  for  density  of  population  and  increase  of  civilization  are  dis¬ 
tributed  in  a  peculiar  fashion.  They  prevail  in  the  highlands,  where  there  is  no  evidence 
that  the  civilization  of  the  past  was  any  higher  than  that  of  the  present;  and  do  not  prevail 
in  the  lowlands,  where  there  is  clear  evidence  of  the  existence  for  many  centuries  of  a 
civilization  far  in  advance  of  that  of  to-day.  Moreover,  the  ancient  civihzation  did  not 
come  to  the  country  full-fledged,  as  did  that  of  Spain  in  later  times.  It  did  not  do  its 
finest  work  at  once  and  then  decline,  as  did  that  of  the  Spaniards  after  they  had  built  their 
massive  old  churches.  On  the  contrary,  it  apparently  arose  where  we  find  its  ruins,  and 
it  endured  for  centuries  before  it  decayed.  The  most  fundamental  fact  is  not  the  great 
change  which  has  taken  place  in  the  character  of  the  Maya  race.  Nor  is  it  the  fall  of  Maya 
civilization,  whether  from  internal  decay  or  external  attack.  It  is  merely  the  simple 
fact  that  the  highest  native  American  civilization  grew  up  in  one  of  the  worst  physical 
enviromnents  of  the  whole  western  hemisphere.  Close  at  hand,  in  the  Guatemalan  high¬ 
lands  on  one  side,  and  in  the  dry  strip  of  northern  Yucatan  on  the  other,  far  more  favorable 
environments  were  occupied  by  closely  allied  branches  of  the  same  race,  but  the  greatest 
civilization  grew  up  in  the  densely  forested,  highly  feverish,  and  almost  untillable  lowlands 
of  Peten  and  eastern  Guatemala. 

The  explanation  of  this  peculiar  state  of  affairs  appears  to  lie  in  one  or  all  of  three  things : 
first,  the  character  of  the  Maya  race;  second,  the  relative  abundance  and  virulence  of  various 
diseases;  and  third,  the  nature  of  the  climate  and  its  effect  on  forests,  diseases,  and  agri¬ 
culture.  It  is  possible  to  adopt  the  usual  unexpressed  assumption  of  historians  and  to 
suppose  that  the  original  Mayas  were  stronger  and  more  virile  than  any  other  race 
which  has  entered  the  torrid  zone,  and  that  because  of  some  unexplained  stimulus,  whose 


GUATEMALA  AND  THE  HIGHEST  NATIVE  AMERICAN  CIVILIZATION. 


223 


nature  it  is  hard  to  surmise,  they  flourished  greatly  in  a  habitat  in  which  modern  races  can 
barely  subsist.  The  theory  that  the  Mayas  were  different  from  other  races  has  a  good  deal 
to  commend  it.  They  certainly  were  a  remarkable  people.  The  only  question  is  how 
remarkable.  The  nearest  analogue  to  their  achievements  is  found  in  the  ruins  of  Indo- 
China,  Ceylon,  and  Java.  In  none  of  these  cases,  however,  was  the  degree  of  success  (as 
measured  by  our  formula  of  achievements  divided  by  opportunities)  anything  like  so  great 
as  among  the  Mayas.  The  Asiatic  races  appear  to  have  been  hke  the  Spaniards,  invaders 
who  did  not  develop  a  new  civilization,  but  brought  their  ideas  with  them  from  other 
places  where  we  can  still  see  remains  of  the  parent  culture;  moreover,  they  did  not  rise  to 
the  height  of  inventing  a  method  of  writing,  and,  in  Indo-China  at  least,  they  had  the 
advantage  of  tools  of  iron.  Nevertheless,  when  their  history  is  finally  understood,  we 
shall  perhaps  ascertain  that  their  civilization  and  that  of  the  Mayas  arose  under  similar 
conditions  because  of  similar  causes.  This,  however,  is  aside  from  the  question.  The 
important  point  is  that  no  matter  how  capable  we  suppose  the  ancient  Ceylonese,  Indo- 
Chinese,  and  Javanese  to  have  been,  the  Mayas  were  still  more  capable,  for  not  only  were 
their  achievements  greater  than  those  of  the  others,  but  their  opportunities  were  less.  Hence, 
if  we  explain  the  rise  of  Maya  culture  solely  on  the  basis  of  racial  character  we  are  forced 
to  assume  that  the  ancient  Mayas  were  not  only  almost  immeasurably  in  advance  of  any 
race  that  now  lives  under  a  similar  environment,  but  were  more  competent  than  any  other 
race  that  has  ever  hved  permanently  in  any  part  of  the  torrid  zone.  Indeed,  in  their 
achievements  in  overcoming  an  adverse  environment,  we  are  perhaps  obliged  to  put  them 
on  a  pinnacle  above  any  other  race  that  has  ever  lived. 

Without  denying  that  the  Mayas  were  a  remarkable  people,  let  us  entertain  the  further 
hypothesis  that  in  the  days  of  their  greatness  tropical  fevers  either  had  not  been  introduced 
into  America,  or  were  by  no  means  so  virulent  as  now.  This  helps  us  greatly,  for  it  relieves 
us  of  the  necessity  of  assuming  the  Mayas  to  have  possessed  a  degree  of  resistance  to  fevers 
far  in  excess  of  anything  known  to-day.  There  are,  however,  grave  objections  to  this 
hypothesis.  In  the  first  place,  it  is  a  pure  assumption  entirely  unsupported  by  any  inde¬ 
pendent  evidence.  In  the  second  place,  tropical  diseases  are  numerous,  and  even  malarial 
fevers  are  of  several  kinds.  We  may  readily  suppose  that  one  or  two  diseases  may  have 
been  introduced  into  Central  America  between  the  time  of  the  Maya  civilization  and  the 
Spanish  Conquest,  but  in  the  entire  absence  of  any  evidence  it  is  a  rather  large  assumption 
to  suppose  that  many  diseases  were  thus  introduced  and  that  they  were  able  to  work  so 
great  a  revolution.  Thirdly,  this  hypothesis  does  not  explain  why  the  advancement  of 
civilization  went  on  so  rapidly  and  for  so  long  in  spite  of  the  enervating  effects  of  almost 
unchanging  heat  and  dampness.  Nor  does  it  explain  why  the  Maya  civilization  reached 
the  coast  at  only  one  or  two  spots.  So  far  as  topography  is  concerned  there  is  nothing  to 
prevent  this  on  either  coast.  Much  of  the  narrow  Pacific  plain  could  be  cultivated  with 
ease,  even  though  swamps  do  cover  part  of  it,  and  on  the  Atlantic  side  the  parts  of  the 
forest  where  there  are  no  ruins  seem  to  be  no  worse  than  those  where  they  exist.  The 
native  inhabitants  of  this  region  all  appear  to  have  been  of  Maya  stock,  even  though  they 
may  not  have  belonged  to  the  main  branch.  Under  such  circumstances  it  hardly  seems  as 
if  so  progressive  a  civilization  could  have  existed  many  centuries  without  extending  its 
influence  to  the  coast  in  British  Honduras,  unless  there  had  been  some  preventive  such  as 
fever. 

The  assumption  that  in  Central  America  tropical  diseases  were  formerly  less  abundant 
or  less  baneful  than  now  relieves  us  of  the  necessity  of  supposing  that  the  Mayas,  remarkable 
as  they  were,  possessed  a  degree  of  immunity  or  resistance  to  disease  far  in  excess  of  that  of 
other  races,  but  it  does  not  relieve  us  of  other  difficulties.  Moroever,  as  it  now  stands  it 
has  the  weakness  of  being  a  pure  assumption  with  no  assignable  cause  and  no  independent 
evidence.  If,  however,  we  supplement  our  assumptions  as  to  the  character  of  the  Mayas 


224 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


and  as  to  the  prevalence  of  disease  by  the  further  assumption  of  climatic  changes  such  as 
have  been  inferred  in  previous  chapters,  practically  all  the  difficulties  vanish.  The  Mayas, 
on  this  supposition,  lived  in  an  environment  as  favorable  as  any  now  found  within  the 
tropics.  They  did  not  suffer  greatly  from  tropical  diseases  because  the  physical  conditions 
were  not  favorable  to  the  propagation  of  harmful  species  of  mosquitoes. 

The  sort  of  climatic  change  which  we  have  inferred  would  involve  the  following  con¬ 
ditions  at  the  height  of  the  Maya  civilization:  In  the  first  place,  the  dry  season  would 
have  been  longer,  more  windy,  and  colder  than  at  present.  This  would  not  have  influenced 
the  coastal  strip  so  much  as  the  interior.  Hence  the  coast  may  have  had  considerable 
forests  or  at  least  dense  jungle,  and  may  have  been  feverish.  Farther  in  the  interior, 
however,  where  the  ruins  are  chiefly  located,  relatively  dry  conditions  would  have  prevailed 
like  those  of  northern  Yucatan  to-day,  save  that  the  contrast  of  seasonal  temperature 
would  have  been  greater.  Thus  the  habitat  of  the  malarial  species  of  mosquitoes  would 
have  been  much  reduced,  and  fevers  would  have  been  to  a  considerable  extent  relegated 
to  the  coastal  forests,  which  therefore  would  have  had  little  population.  In  addition  to 
this  the  enervating  influence  of  climatic  uniformity  would  have  been  somewhat  reheved, 
and  agriculture  of  the  intensive  kind  would  have  been  possible  in  the  Peten  plain,  just  as 
it  is  to-day  in  northern  Yucatan.  The  areas  of  big  jungle  where  life  is  excessively  easy 
so  long  as  the  population  remains  uncivilized  and  comparatively  scanty,  but  where  intensive 
agriculture  is  to-day  difficult,  would  have  been  much  reduced.  Thus  the  Peten  region, 
being  a  fertile  lowland,  would  have  been  a  natural  center  of  civilization.  In  other  words, 
the  adoption  of  the  climatic  hypothesis  does  not  lead  us  to  abandon  our  hypotheses  as  to 
racial  character  and  disease.  It  merely  removed  from  them  certain  elements  of  improb¬ 
ability.  It  supplies  the  elements  which  the  other  hypotheses  lack,  and  in  addition  it 
possesses  the  strength  of  being  supported  by  strong  external  evidence. 

In  this  last  statement  lies  the  chief  significance  of  the  present  chapter.  Our  climatic 
hypothesis  was  framed,  crudely  at  first,  in  Russian  Turkestan  and  Persia;  it  was  revised  in 
Chinese  Turkestan  and  India;  modified  greatly  by  studies  in  Palestine  and  Asia  Minor, 
and  confirmed  apparently  by  the  burial  of  Olympia,  by  the  distribution  of  population  in 
Greece,  and,  so  it  seems,  by  what  others  describe  in  North  Africa.  It  was  further  con¬ 
firmed,  but  again  much  modified,  by  ruins  in  the  southwestern  United  States  and  by  the 
trees  of  California.  Finally,  it  was  applied  to  the  torrid  zone  in  Yucatan  and  seemed  to 
fit  the  facts.  Now  it  has  been  carried  to  another  tropical  region  where  a  fuller  test  is 
possible.  Here  again,  down  to  such  minute  details  as  small  fluvial  terraces,  it  seems  to 
be  in  accordance  with  the  facts.  Doubtless  it  will  be  further  modified;  doubtless  I  have 
ascribed  to  it  some  results  really  due  to  other  causes,  but  that  is  an  inevitable  stage  of  a 
new  subject.  The  only  question  is,  how  far  does  the  present  theory  harmonize  with  the 
great  body  of  facts  by  which  it  has  been,  or  may  in  future,  be  tested?  So  far  as  it  does, 
we  may  tentatively  accept  it.  So  far  as  it  does  not,  it  must  be  revised. 


CHAPTER  XVIII. 


CLIMATIC  CHANGES  AND  MAYA  HISTORY. 

As  a  last  step  in  our  investigation  of  climatic  changes  in  Central  America  let  us  briefly 
consider  Maya  history  and  see  how  the  future  elucidation  of  this  most  perplexing  subject 
will  either  disprove  certain  parts  of  onr  hypothesis,  or  else  greatly  strengthen  them.  Let 
us  first  state  what  expectations  the  hypothesis  would  lead  to  and  then  compare  them  with 
the  conclusions  of  the  best  authorities  on  Maya  history.  For  the  thousand  years  previous 
to  the  time  of  Christ,  to  judge  from  figure  50,  on  page  172,  the  general  climatic  conditions 
were  such  that  in  subtropical  regions,  like  central  California  or  Palestine,  the  driest  times 
were  as  moist  as  the  wettest  times  are  at  present.  This  seems  to  mean  a  pronounced  dis¬ 
placement  of  the  zone  of  westerly  storms  toward  the  south,  especially  in  winter.  Therefore 
in  winter  the  whole  Maya  country  probably  had  a  long  dry  season  comparable  to  that  which 
now  prevails  only  in  the  relatively  progressive  region  of  northern  Yucatan.  Under  such  cir¬ 
cumstances  jungle  rather  than  forest  would  be  the  prevalent  growth  over  the  whole  area,  and 
the  contrast  between  summer  and  winter  would  be  greater  than  it  is  now  in  any  part  of  the 
country.  Thus  the  two  chief  drawbacks  to  civilization,  namely,  the  feverish,  irreclaimable 
forests  and  the  deadening  climatic  monotony,  would  be  in  part  removed.  A  thousand  years 
of  such  conditions  would  give  opportunity  for  the  growth  of  civilization,  which  we  should 
expect  to  find  making  rapid  strides  from  the  sixth  to  the  fourth  century  b.  c.,  falling  off  then 
somewhat  for  200  years,  rising  again  during  the  second  century,  and  continuing  at  a  high  level 
for  200  to  300  years.  Then  from  200  a.  d.  to  650  a.  d.,  as  appears  in  figure  72  on  page  209, 
which  is  merely  a  part  of  figure  50  with  an  enlarged  vertical  scale,  the  general  tendency  would 
be  downward,  with  an  interruption  perhaps  in  the  sixth  century,  but  reaching  a  very  low 
ebb  in  the  seventh.  The  long  decline  of  the  California  curve  of  figure  50  from  soon  after 
the  time  of  Christ  to  650  a.  d.,  it  must  be  remembered,  is  probably  more  important  than 
the  apparently  sharper  and  greater  declines  of  earlier  times,  for  those  are  exaggerated 
because  of  the  small  number  of  trees  available  more  than  2,000  years  ago.  During  the 
decline  after  the  time  of  Christ  the  southern  parts  of  Maya  land  would  suffer  first  and 
might  so  far  revert  to  true  forest  as  to  become  uninhabitable  by  any  one  except  wandering 
savages,  while  the  northern  parts  would  still  possess  comparatively  favorable  conditions. 
In  the  seventh,  eighth,  and  ninth  centuries  we  should  expect  that  conditions  would  be 
no  better  than  at  present.  Forests  would  natmally  prevail  wherever  they  are  now  found, 
the  area  where  civilization  is  possible  would  be  restricted  to  northern  Yucatan,  and  the 
people  would  be  steadily  weakened  by  fevers  and  a  warm,  monotonous  climate.  Before 
their  energy  was  wholly  sapped,  however,  and  before  the  ancient  culture  had  completely 
disappeared,  improved  conditions,  beginning  about  880  a.  d.  and  lasting  two  centuries, would 
cause  a  revival;  the  forest  belt  would  be  pushed  back  somewhat,  but  not  so  far  by  any 
means  as  at  the  time  of  Christ,  and  for  a  time  the  greater  contrast  of  the  seasons  would 
help  to  stimulate  the  people.  Then  would  follow  a  decline  culminating  about  1300  a.  d. 
At  the  beginning  of  the  fourteenth  century  another  revival  of  culture  might  be  expected, 
but  it  would  be  of  slight  importance  for  two  reasons:  In  the  first  place,  the  adverse  con¬ 
ditions  of  the  twelfth  and  thirteenth  centuries  would  probably  have  reduced  the  jungle- 
covered  area  to  small  extent  and  would  have  brought  the  vigor  of  the  people  to  a  condition 
even  lower  than  was  reached  in  the  preceding  adverse  period.  In  the  second  place,  the 
favorable  period  is  limited  to  about  a  hundred  years,  chiefly  during  the  fourteenth  century, 
too  short  a  time  to  produce  very  pronounced  effects.  Then  would  come  a  third  relapse, 

16  225 


226 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


which  would  probably  bring  the  people  to  a  lower  state  than  ever  by  1500  a.  n.,  just  before 
the  Spaniards  arrived.  Since  that  time  a  slight  but  unimportant  recovery  might  be  looked 
for,  but  its  magnitude  would  depend  on  whether  our  sequoia  curve  should  lie  in  the  upper 
or  lower  of  the  two  positions  indicated  in  figure  72. 

Before  comparing  this  inferred  history  with  that  which  actually  occurred,  two  signals  of 
warning  must  be  set  up.  In  the  first  place,  I  would  not  be  understood  to  imply  that  climatic 
changes,  with  their  attendant  physiological,  pathological,  economic,  and  political  results, 
are  the  only  or  main  cause  of  historic  events.  Doubtless  races,  like  individuals,  go  through 
a  definite  development  from  youth  to  maturity  and  old  age.  Doubtless  such  circumstances 
as  luxury,  contact  with  other  races,  the  introduction  of  new  ideas,  and  the  commanding 
genius  of  gifted  individuals  are  so  important  that  any  one  of  them  may  completely  reverse 
the  effects  of  physical  environment.  Nevertheless,  the  environment  continues  to  act. 
An  injurious  change,  like  a  slow,  wasting  sickness,  may  perhaps  cause  a  youthful  nation 
to  age  prematurely,  while  a  beneficial  change,  like  the  cure  of  a  chronic  disease,  may 
restore  a  youthful  buoyancy  which  had  seemed  to  be  forever  lost.  These  things  will  not 
change  the  laws  of  the  rise  and  decay  of  nations,  nor  will  they  nullify  the  effect  of  ideas, 
inventions,  genius,  and  the  thousand  other  factors  which  enter  into  history.  The  case  is 
exactly  like  that  of  a  human  being.  Nothing  can  prevent  him  from  passing  from  youth 
to  maturity  and  old  age;  sickness  need  not  necessarily  prevent  him  from  enjoying  the 
advantages  and  stimulus  of  friendship,  reading,  and  travel;  a  new  interest  may  temporarily 
or  even  permanently  overcome  a  physical  weakness  that  has  hitherto  prostrated  him, 
and  he  may  die  in  his  youth  and  strength  through  accident,  or  may  linger  on  to  extreme 
old  age  in  spite  of  chronic  illness.  Yet  all  these  things  do  not  mean  that  disease  has  no 
effect  or  that  it  is  not  highly  important.  And  so  it  is  with  physical  environment;  favor¬ 
able  conditions  will  not  make  a  stupid  race  brilliant,  nor  will  unfavorable  conditions  destroy 
the  natural  abilities  of  a  race  that  is  gifted.  Nevertheless,  changes  of  climate,  like  the 
coming  and  going  of  disease,  may  help  or  hinder  the  progress  or  decline  which  is  taking 
place  as  the  result  of  the  complex  interplay  of  all  the  many  factors  that  control  historic 
development. 

Our  second  warning  signal  is  necessitated  by  the  extreme  scantiness  of  our  knowledge  of 
early  Maya  history.  The  chief  sources  of  knowledge  are,  first,  certain  chronicles  which  were 
pieced  together  after  the  arrival  of  the  Spaniards  and  were  written  in  the  Maya  language 
but  with  Spanish  letters.  They  pertain  only  to  northern  Yucatan  and  are  often  confused 
and  inaccurate,  but  have  a  distinct  historical  value.  A  second  but  as  yet  unusable  source 
of  knowledge  is  three  or  four  codices  of  pre-Spanish  date  written  in  Maya  hieroglyphics, 
but  the  key  to  their  interpretation  has  not  been  found  and  the  only  intelligible  portion  is 
certain  calculations.  Many  such  codices  existed  at  the  time  of  the  Spanish  conquest,  but 
the  conquerors,  in  their  zeal  for  rehgion,  burned  all  they  could  lay  their  hands  upon.  A 
third  source  of  knowledge  is  a  considerable  number  of  stelae,  hntels,  and  other  monuments, 
found  in  connection  with  temples  and  bearing  dates  according  to  the  old  Maya  calendar. 
These,  unfortunately,  are  confined  to  the  southwestern  portion  of  Maya  land,  and  only  one 
or  two  have  been  found  in  northern  Yucatan.  The  most  important  is  upon  a  lintel 
at  Chichen  Itza,  the  greatest  city  of  the  region.  Finally,  our  best  knowledge  of  the  Mayas 
is  derived  from  the  nature  and  development  of  their  art  and  architecture,  a  subject  which 
has  been  carefully  investigated  by  Mr.  H.  J.  Spinden,  in  his  recent  work,  ‘‘A  Study  of 
Maya  Art.”*  He  there  sums  up  the  evidence  derived  from  the  various  sources  of  knowledge 
and  displays  it  graphically  in  a  chronological  table.  Unfortunately,  however,  the  study 
of  art  and  architecture  does  not  furnish  exact  dates.  Therefore  we  still  remain  in  great 
uncertainty  as  to  all  but  the  main  outlines  of  Maya  history,  and  the  statements  which 
follow  must  be  regarded  as  largely  tentative. 


*  Memoirs  of  the  Peabody  Museum  of  American  Archaeology  and  Ethnology,  Harvard  University,  1913. 


CLIMATIC  CHANGES  AND  MAYA  HISTORY. 


227 


The  paramount  difficulty  in  Maya  history  is  the  correlation  of  the  ancient  and  recent 
Maya  calendars  with  one  another  and  with  the  European  system  of  chronology.  The 
complexity  of  the  matter  may  be  illustrated  by  the  fact  that  the  date  of  Stela  9  at 
Copan  is  interpreted  by  Seler  as  1255  b.  c.,  by  Bowditch  as  34  a.  d.,  and  by  Morley  as 
288  A.  D.  The  trend  of  recent  opinion  seems  to  be  that  Seler’s  date  is  much  too  early, 
but  the  entire  matter  is  still  an  open  question.  The  ancient  Mayas  who  built  the  ruins 
and  the  modern  ones  who  wrote  the  chronicles  just  after  the  Spanish  invasion  used  the 
same  highly  complex  calendar,  but  with  slightly  different  adjustments  and  varying  degrees 
of  completeness.  The  major  units  of  this  calendar  were  the  “tun,”  having  a  length  of 
360  days;  the  “katun,”  consisting  of  20  tuns;  and  the  cycle,  composed  of  20  “katuns,” 
or  approximately  398  years.  According  to  the  ancient  method  every  date  consisted  of  5 
numbers,  indicating  the  cycle,  katun,  tun,  month,  and  day.  In  later  times  this  cumbersome 
method  was  abandoned  and  seems  to  have  passed  out  of  use  several  centuries  before  the 
coming  of  Europeans.  An  abbreviated  system  was  in  use  at  the  time  of  the  Spanish  con¬ 
quest  and  the  great  problem  of  Maya  chronology  is  to  correlate  this  with  the  ancient  system 
and  with  the  European  chronology.  One  of  the  peculiarities  of  both  ancient  and  later 
calendars  was  that  each  katun  or  20-year  period  began  with  a  day  called  “Ahau.”  The 
Ahau  was  a  sequence  of  13  days,  and  different  days  were  designated  as  1  Ahau,  2  Ahau,  etc. 
It  so  happened  that  the  Ahau  days  with  which  successive  katuns  began  fell  in  the  following 
sequence:  13,  11,  9,  7,  5,  3,  1,  12,  10,  8,  6,  4,  2.  Among  the  later  Mayas  the  dates  were 
simply  indicated  by  giving  the  number  of  the  day  Ahau  with  which  the  given  katun 
began.  Hence,  while  the  old  method  fixed  the  date  for  all  time,  provided  the  year  1 
were  definitely  known,  the  later  method  only  fixed  its  relative  position  in  the  period  of 
260  years  making  up  the  13  katuns  of  a  single  series  of  katuns  beginning  with  the  13 
Ahau  days.  It  is  as  if  we  were  to  abandon  the  use  of  the  numbers  indicating  centuries 
in  our  era  and  to  write  only  the  last  two  figures  of  our  dates.  If  we  did  this  we  should 
know  that  the  years  ’20  and  ’50  were  30  years  apart,  provided  that  they  fell  in  the  same 
century,  but  if  we  had  two  such  dates  and  did  not  know  their  centuries  one  might  be  1220 
and  the  other  1550.  Thus  in  using  the  later  Maya  calendar  great  care  must  be  exer¬ 
cised  in  order  not  to  confuse  the  various  260-year  periods,  for  otherwise  the  chronology 
becomes  utterly  unreliable  and  the  time  of  any  event  may  be  displaced  by  260  years  or  by 
some  multiple  of  260. 

Maya  chronology,  as  Spinden  expresses  it,  “rests  upon  a  tripod  foundation,  one  leg 
being  the  chronicles  preserved  after  the  coming  of  the  Spaniards,  another  leg  being  the 
inscribed  dates,  and  the  third  being  the  natural  order  of  art  and  architecture.  The  earliest 
period  is  strong  through  the  practical  coincidence  of  the  inscribed  dates  and  the  natural 
order  of  the  art.  The  latest  part  of  the  history  is  equally  certain  on  account  of  the  fullness 
of  the  traditions.  The  intermediate  period  is  the  only  one  which  as  yet  has  been  incapable 
of  strong  reinforcement.”  The  traditional  history  of  the  Mayas  was  recorded  in  the  Maya 
language,  but  in  Spanish  letters  not  long  after  the  Conquest.  It  is  fairly  full  for  later  times, 
but  of  course  becomes  less  and  less  dependable  as  we  go  farther  into  the  past.  Its  dates  are 
given  in  the  abbreviated  later  style,  but  as  this  was  still  used  at  the  coming  of  the  Spaniards 
the  dates  can  of  course  easily  be  determined  in  the  European  calendar.  Farther  back  the 
danger  of  mistakes  greatly  increases,  but  for  five  or  six  centuries  it  does  not  become  serious, 
for  the  errors  must  amount  to  260  years,  and  so  are  easily  avoided.  Back  of  about  900 
A.  D.,  however,  the  traditions  become  scanty  and  confused  and  the  possibility  of  errors 
increases  enormously.  The  traditional  history  is  connected  with  that  of  the  dated  monu¬ 
ments  only  most  vaguely.  For  example,  it  refers  to  the  “discovery”  of  Chichen  Itza  and 
to  its  abandonment  and  reoccupation,  but  at  Chichen  Itza  only  a  single  date  has  been  found, 
upon  a  lintel.  This  lintel  does  not  seem  to  be  in  its  original  position,  but  to  have  been 
rebuilt  into  a  new  structure  after  the  old  one  had  fallen  to  ruins. 


228 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Turning  now  to  the  ancient  monuments,  the  dates  on  these  are  all  given  in  the  full  form, 
including  the  cycle,  katun,  and  tun.  Hence  they  can  be  placed  with  precision  in  their 
relation  to  one  another.  The  only  difficulty  lies  in  reading  them,  for  being  inscribed  chiefly 
upon  soft  limestone  they  are  in  many  cases  so  worn  that  it  is  difficult  to  decipher  them,  and 
various  authorities  often  disagree  in  this  matter.  Nevertheless,  it  is  fairly  easy  to  elucidate 
the  chronology  of  several  centuries  during  which  monuments  are  abundant.  If  a  single 
date  recorded  according  to  the  ancient  system  could  be  unmistakably  correlated  with  our 
European  calendar  the  problem  of  dating  the  monuments  would  be  solved.  In  one  case 
the  date  of  the  death  of  a  chief  named  Ahpula,  who  died  in  1536  a.  d.,  has  been  recorded  in 
this  way  in  a  manuscript  written  after  the  coming  of  the  Spaniards,  Bowditch,*  one  of  the 
best  authorities  on  the  Maya  calendar,  considers  that  this  is  the  most  reliable  link  between 
the  European  calendar  and  the  monuments.  There  are  various  difficulties,  however,  and 
the  matter  is  by  no  means  so  simple  as  it  appears.  For  example,  in  late  Maya  times  the 
position  of  each  day  in  its  month  had  somehow  been  slightly  shifted  from  its  position  in  the 
inscriptions,  and  we  are  uncertain  just  what  effect  this  may  have  had  on  the  count.  The 
other  chief  method  of  determining  the  relation  of  the  dates  on  the  monuments  to  the 
European  calendar  is  that  followed  by  Morley.  On  the  basis  of  tradition  he  determines  the 
probable  date  of  the  two  occupations  of  Chichen  Itza.  The  date  on  the  lintel  there  is 
read  as  the  second  katun  of  the  tenth  cycle,  or  katun  3  Ahau,  according  to  the  later  system. 
The  problem  then  becomes  to  find  a  period  of  occupation  that  includes  the  katun  3  Ahau. 
Morley  solves  this  by  putting  the  date  in  the  first  period  of  occupation,  which  also  seems 
to  be  the  only  possible  position  for  architectural  reasons.  The  resulting  coincidences  are 
regarded  by  Spinden  as  so  remarkable  that  he  considers  that  they  solve  the  question  of 
Maya  chronology,  but  this  opinion  is  by  no  means  universally  shared  by  archaeologists. 
To  the  layman  it  seems  as  if  Bowditch  had  employed  the  most  reliable  method  of  deter¬ 
mining  the  relation  of  the  dates  on  the  monuments  to  the  European  calendar,  while  tradi¬ 
tional  dates  seem  to  be  the  only  way  of  arriving  at  the  chronology  of  the  period  after  the 
last  monuments.  The  artistic  sequence,  on  the  other  hand,  is  highly  valuable  at  all  times 
as  a  check  upon  the  others  and  as  a  means  of  bridging  the  gap  where  no  other  information 
is  available. 

Leaving  now  this  intricate  problem  of  Maya  chronology,  let  us  briefiy  review  the  history 
of  the  country.  Perhaps  the  most  convenient  summary  is  given  in  Spinden’s  guide  to  the 
Mexican  Hall  of  the  American  Museum  of  Natural  History  in  New  York.  The  accuracy 
of^his  dates,  as[we  have  already  indicated,  can  not  yet  be  determined,  but  as  to  the  general 
sequence  of  events  there  is  substantial  agreement.  The  earliest  date  yet  found  upon  any 
piece  of  Maya  w'ork  is  recorded  on  the  so-called  Tuxtla  statuette.  Its  decipherment  is 
doubtful.  Morley  makes  it  about  113  b.  c.,  Bowditch  about  365  b.  c.,  and  Seler  nearly  1,300 
years  earlier  than  Bowditch.  The  next  date  is  found  upon  the  so-called  Leiden  plate.  It 
probably  falls  about  160  years  after  that  of  the  Tuxtla  statuette,  and  can  be  read  with  much 
greater  certainty.  These  two  dates  indicate  that  at  least  a  centmy,  and  perhaps  sixteen 
or  seventeen  centuries,  before  the  beginning  of  the  Christian  era  the  Mayas  had  reached  so 
high  a  state  of  civilization  and  had  so  long  preserved  exact  records  of  the  movements  of  the 
sun  and  stars  that  they  had  framed  a  calendar  more  exact  than  any  used  in  Europe  or  Asia 
until  the  adoption  of  the  Gregorian  calendar  in  1582  a.  d.  To  accomplish  this  they  must 
for  many  years  have  been  able  to  record  their  observations  in  permanent  form.  Hence 
we  must  conclude  that  for  centuries  prior  to  375  b.  c.,  to  use  Bowditch’s  dates,  the  Mayas 
had  been  a  highly  progressive  and  intelligent  people. 

About  a  hundred  years  after  the  date  of  the  Leiden  plate  the  Maya  civilization  had 
reached  so  high  a  development  that  important  cities  began  to  arise  in  the  south,  especially 

*C.  P.  Bowditch,  Memoranda  on  the  Maya  calendars  used  in  the  books  on  Chilan  Balam,  American  Anthropol¬ 
ogist,  n.  s.,  vol.  3,  1901,  pages  129  to  138. 


CLIMATIC  CHANGES  AND  MAYA  HISTORY. 


229 


such  places  as  Tikal,  Copan,  and  Quirigua.  Great  temples  were  erected  upon  enormous 
mounds,  and  public  squares  were  adorned  with  stelae  and  altars.  The  earliest  dated  monu¬ 
ment,  according  to  Morley  and  Spinden,  is  Stela  3  at  Tikal,  to  which  Morley  assigns  the 
date  214  a.  d.  The  next  is  at  Copan,  where  Stela  15  was  erected  37  years  later  than  the 
Tikal  stela.  According  to  Bowditch,  however,  Quirigua  is  decidedly  older  than  Copan. 
He  considers  that  Stela  C  at  Quirigua  dates  from  75  b.  c.  and  that  Stela  K,  the  last  stela 
at  that  place,  bears  the  date  275  a.  d.  The  monuments  at  Copan,  on  the  other  hand,  are 
held  by  him  to  range  from  Stela  9,  34  a.  d.,  to  Stela  N,  231  a.  d.  When  Hewett*  began  to 
excavate  at  Quirigua,  however,  the  first  temple  which  he  uncovered  proved  to  have  been 
built  five  years  after  the  erection  of  the  last  monument,  and  other  temples  may  have  been 
erected  still  later. 

In  all  of  these  earlier  sites  the  older  monuments  are  crude  and  archaic,  but  the  style 
grows  gradually  better  and  apparently  culminates  at  about  the  time  of  the  erection  of  the 
last  monuments.  During  the  later  part  of  the  period  when  these  great  cities  flourished 
in  the  south  of  Maya  land,  many  others  sprang  up  in  the  region  farther  north,  for  example, 
Seibal,  Yaxchilan,  Piedras  Negras,  and  Palenque.  These  apparently  never  reached  quite 
so  high  a  stage  of  culture  as  the  earlier  cities.  Their  architecture  may  be  more  striking, 
but  the  carving  on  the  monuments  is  not  so  truly  refined  and  skilful.  They  seem  to  indicate 
that  toward  the  close  of  the  period  of  greatest  Maya  development  there  was  a  gradual 
northward  movement  of  civilization,  accompanied  by  the  beginnings  of  decline. 

Soon  after  600  a.  d.  according  to  Morley  and  Spinden,  or  after  350  a.  d.  according  to 
Bowditch,  the  decline  of  Maya  civilization  culminated  in  a  serious  collapse.  The  southern 
cities  were  apparently  completely  deserted,  for  as  yet  we  have  no  evidence  of  any  long 
occupation  after  the  time  of  the  latest  dated  inscriptions.  Only  in  northern  Yucatan  does 
any  semblance  of  civilization  appear  to  have  remained.  There  Chichen  Itza  appears  to 
have  been  founded  at  about  this  time,  or  at  least  a  certain  amount  of  building  was  going 
on  there,  since  we  have  a  lintel  which  bears  a  date  which  Morley  interprets  as  603  a  d., 
and  which  according  to  Bowditch’s  system  would  fall  about  350  a.  d.  Yet  even  in  the 
north,  Maya  civilization  seems  to  have  been  at  an  extremely  low  ebb,  and  there  was  ap¬ 
parently  little  improvement  until  almost  the  beginning  of  the  tenth  century.  Doubtless 
many  buildings  were  erected  in  northern  Yucatan  during  the  intervening  centuries,  but 
they  must  have  been  comparatively  unimportant,  since  scarcely  a  trace  of  them  has  been 
found.  This  period  may  well  be  called  the  Dark  Ages  of  Maya  history,  although  a  later 
period,  just  before  the  Spanish  Conquest,  was  perhaps  equally  dark.  The  Dark  Ages  were 
followed  by  a  marked  revival.  The  date  of  this  can  not  be  determined  from  monuments, 
but  only  from  the  traditional  accounts,  for  the  Mayas  of  the  Renaissance,  as  we  may  call 
this  period,  did  not  date  their  monuments  and  temples  with  the  care  used  by  their  an¬ 
cestors.  Nevertheless,  it  seems  fairly  certain  that  the  tenth  and  eleventh  centuries  were 
the  time  of  the  erection  of  the  truly  remarkable  series  of  great  buildings  whose  ruins  even 
now  excite  our  wonder  in  northern  Yucatan.  Chichen  Itza  was  apparently  re-established 
at  this  time  after  a  period  of  desertion.  Uxmal  and  Mayapan  were  also  built,  and  these 
three  cities  formed  a  league.  Many  other  towns,  such  as  Kabah,  Labna,  Sayal,  and  Izamal, 
seem  also  to  have  flourished,  but  we  have  no  traditions  of  any  except  Izamal.  The  archi¬ 
tectural  remains  of  this  period  are  to-day  the  most  imposing  ruins  in  any  part  of  the  Western 
Hemisphere.  Nevertheless,  although  they  appear  more  impressive  than  those  of  earlier 
times,  they  do  not  represent  so  high  a  type  of  architecture.  Stelae  and  other  carved  monu¬ 
ments,  for  example,  are  almost  unknown,  and  easily  prepared  wooden  lintels  are  substituted 
for  the  more  laboriously  prepared  stone  type.  New  ideas  are  not  so  abundant  as  formerly, 
and  the  general  aspect  is  that  of  the  revival  of  an  earlier  art  without  its  originality. 

*Edgar  L.  Hewett,  Two  Seasons’  Work  in  Guatemala,  Proceedings  of  the  Archeological  Institute  of  America,  June 

1911,  pp.  117-134.  The  Third  Season’s  Work  in  Guatemala,  ditto,  June  1912,  pp.  163-171. 


230 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Another  noticeable  feature  is  that  the  culture  of  this  time  did  not  persist  long.  By 
1,200  A.  D.  or  earlier,  serious  civil  wars  appear  to  have  broken  out,  and  in  general  a  period 
of  relative  instability  ensued.  Spinden  describes  this  period  as  follows : 

“After  the  fall  of  Mayapan  the  Mayas  seem  to  have  been  divided  into  many  warring  fac¬ 
tions.  All  the  great  cities  were  abandoned,  although  the  temples  were  still  regarded  as  sacred.  Of 
course,  stonebuilt  architecture  was  still  prevalent,  as  we  know  from  some  of  the  early  descriptions 
of  towns  on  the  coast.  Learning  was  still  maintained  by  the  nobles  and  the  priests.  But  there 
was  not  the  centralized  authority  necessary  for  the  keeping  up  of  such  luxuriant  capitols  as  existed 
in  the  old  days.  At  the  present  time  certain  ancient  ideas  still  persist,  as  has  already  been  stated 
in  connection  with  the  ethnology  of  the  Lacandone  Indians.  Upon  the  western  highlands  there 
is  another  body  of  traditions  which  concern  the  Quiche,  Cakohiquel,  and  other  Mayan  tribes,  but  do 
not  go  back  for  more  than  200  years  before  the  Spanish  Conquest  and  are  of  very  little  real  service. 
All  in  all  there  is  little  to  be  said  in  favor  of  the  frequent  plaint  that  the  coming  of  the  white  man 
snuffed  out  a  culture  that  promised  great  things.  The  golden  days  of  the  Maya  civilization  had 
already  passed,  and,  if  we  may  judge  by  the  history  of  other  nations,  would  never  have  returned.” 

To  sum  up  the  whole  matter,  the  outstanding  facts  in  Maya  history  seem  to  be  as 
follows :  First,  we  have  a  long  period  of  active  development,  during  which  the  calendar  was 
evolved,  and  the  arts  of  architecture  and  sculpture  were  gradually  developed,  although  few 
tangible  evidences  of  this  now  remain.  This  time  of  marked  growth,  according  to  all 
authorities,  must  have  preceded  the  Christian  era.  Then  comes  a  period  when  the  previous 
development  flowered,  as  it  were,  in  the  building  of  the  great  cities  of  Copan,  Quirigua, 
Tikal,  and  presumably  many  others  less  well  known.  These  first  great  cities  were  in  the 
southern  part  of  the  Maya  area,  on  the  borders  of  Honduras,  or  in  eastern  Guatemala. 
They  lasted  perhaps  three  or  four  centuries,  and  then  quickly  declined.  So  far  as  we  have 
any  evidence,  civilization  never  revived  in  this  southern  area,  for  the  structures  of  the  great 
period  have  not  been  rebuilt  by  later  inhabitants.  Toward  the  end  of  the  period  of  great¬ 
ness  the  center  of  Mayan  culture  moved  northward  into  northern  Peten  and  the  Mexican 
provinces  of  Tabasco,  Chiapas,  and  Yucatan.  The  great  period,  according  to  Bowditch, 
lasted  from  approximately  100  b.  c  to  350  a.  d.  The  more  northern  cities,  perhaps, 
flourished  a  little  after  this  time,  but  not  for  long.  Then  there  came  a  time  of  very  low 
civilization,  lasting  for  centuries.  Apparently  during  these  dark  ages  northern  Yucatan 
was  the  only  place  where  civilization  survived.  A  revival  ensued  about  900  or  1,000  years 
after  Christ,  and  architecture  once  more  reached  a  high  pitch.  Yet  there  was  no  such 
originality  as  during  the  earlier  period,  and  marked  progress  was  made  only  in  northern 
Yucatan  :  all  the  rest  of  the  country  seems  to  have  remained  in  darkness.  Moreover,  this 
mediaeval  revival  was  relatively  short-lived.  We  do  not  know  its  exact  duration,  but 
apparently  most  of  the  important  buildings  were  erected  within  the  space  of  one  or  two 
centuries.  Since  that  time  the  condition  of  the  Mayas  has  fluctuated  more  or  less,  but  on 
the  whole  there  has  been  a  dechne. 

Already  the  reader  has  doubtless  seen  that  the  general  history  of  the  Mayas,  in  its 
broader  features,  agrees  with  what  we  should  expect  from  the  pulsatory  theory  of  climatic 
changes;  that  is,  there  have  been  alternate  periods  of  growth  and  decline,  which  occur  in 
just  the  way  that  we  should  expect  on  the  supposition  that  changes  of  climate  have  been 
an  important  factor  in  determining  whether  civilization  was  possible  or  not.  If  Bowditch’s 
method  of  dating  Maya  chronology  is  correct,  times  of  favorable  climatic  conditions,  as 
indicated  by  our  California  trees,  have  also  been  times  when  the  Mayas  reached  a  high 
stage  of  civilization.  If  the  system  of  Seler  is  correct,  there  is  probably  also  the  same  kind 
of  agreement,  although  this  has  not  yet  been  carefully  tested.  If  Morley  and  Spinden  are 
correct,  on  the  other  hand,  the  events  of  Maya  history  since  600  a.  d  agree  quite  closely 
with  our  expectations,  but  previous  to  600  a.  d.  the  agreement  holds  only  imperfectly. 
For  the  sake  of  convenience,  the  whole  matter  is  summed  up  briefly  in  Table  12.  The 


HUNTINGTON 


PLATE  12 


A.  Stelae  inscribed  with  hieroglyphics  at  Quirigua;  dense  tropical  forest  in  background. 

B.  The  ruins  of  Copan.  When  discovered  the  rums  were  covered  with  large  trees  like  those  on  the  right.  The  mounds  in 

the  middle  foreground  are  the  mam  rums.  r 


X' 


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WTi, 


:•  ♦•'A+.i 


■A-., 


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1 

';:.V1., 

•  • 

•  .  '  '  i " 

•  V 

ft 

h 

, .  i  '■>! 

/••Ir'v- 

■  *  1  • 

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‘.'•i  V  ■■ 

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'.'4^.'irdrA,'J 


■  • 


CLIMATIC  CHANGES  AND  MAYA  HISTORY. 


231 


dates  are,  of  course,  only  approximate.  They  are  given  according  to  Bowditch’s  system. 
Figure  72  is  repeated  in  order  that  it  may  be  available  for  direct  comparison  with  the  table. 

No  great  weight  rnust  be  attached  to  the  general  agreement  which  this  table  seems  to 
show  between  climatic  pulsations  and  the  history  of  the  Mayas.  In  the  first  place,  the 
agreement  does  not  apply  to  details,  and  in  all  probability  no  amount  of  investigation  is 
ever  likely  to  show  that  it  does  so  apply .  In  the  second  place,  so  long  as  Mayan  chronology 
is  so  uncertain  we  can  not  lay  much  weight  upon  it.  The  chief  reason  for  introducing  the 
matter  is  to  point  out  one  of  the  ways  in  which  the  study  of  climate  may  cooperate  with 
archeology  and  history,  and  each  may  be  used  as  a  check  upon  the  other.  In  the  course  of 


Table  12. 


Period. 

Date. 

j  Inferred  climatic  conditions  in  Maya  land. 

1  Historical  conditions  in  Maya  land. 

1 

1000-400  B.  c. 

1  Prouounced  dry  winter  season  everywhere,  strong 
contrast  of  seasons,  few  dense  forests,  conditions 

1  much  more  stimulating  than  now. 

Period  of  developing  culture  and  great  progress. 

2 

400-100  B.  c. 

Similar  to  (1)  but  not  quite  so  strong  a  contrast  of 
seasons. 

Period  of  first  known  artistic  work.  Not  essen¬ 
tially  different  from  (1). 

3 

100  B.  C.-300  A.  D. 

Intermediate  between  (1)  and  (2),  but  beginning  to 
become  less  favorable  toward  the  end  of  the  period, 
especially  in  the  south. 

Period  of  high  culture  beginning  in  the  south  and 
progressing  northward.  By  the  end  of  the 
period  great  architectural  works  had  ceased  in 
the  south  but  not  in  the  center. 

4 

300—150  A.  D. 

Steady  increase  of  unfavorable  conditions.  The  dry 
season  must  have  largely  disappeared  in  the  south 
and  dense  forests  must  have  tended  to  appear  when¬ 
ever  cultivation  was  relaxed. 

Extinction  or  great  decline  of  southern  civiliza¬ 
tion.  The  center  of  activity  moved  to  northern 
Yucatan,  where  it  is  now  located;  but  there  is 
no  evidence  of  any  such  state  of  activity  as  had 
formerly  prevailed  in  the  south. 

5 

450-900  A.  D. 

Highly  unfavorable  conditions,  part  of  the  time  no 
better  than  those  of  to-day  and  at  times  worse. 
Forests  probably  prevailed  everywhere  except  in 
the  narrow  strip  of  northern  Yucatan. 

The  Dark  Ages  of  Maya  history.  Civilization  at 
a  low  ebb.  No  evidence  of  any  great  archi¬ 
tectural  or  other  activity. 

6 

900-1100  A.  D. 

Partial  return  to  favorable  conditions  of  early  periods, 
but  not  enough  to  influence  the  southern  part  of 
Maya  land. 

Pronounced  revival  of  culture,  great  architectural 
and  other  activities,  but  only  in  northern 
Yucatan,  that  is,  in  the  present  dry  area  and 
its  immediate  neighborhood. 

7 

1100-1300  A.  D. 

Return  to  unfavorable  conditions  about  like  those  of 
to-day. 

Renewed  decline  of  civilization.  Frequent  wars 
and  invasions.  End  of  the  era  of  building; 
abandonment  of  great  cities. 

8 

1300-1450  A.  D. 

Second  partial  return  to  favorable  conditions,  like 
(6),  but  not  quite  so  favorable. 

Continued  decline  of  civilization,  no  evidence  of 
any  genuine  recovery. 

9 

1450-1900  A.  D. 

General  continuance  of  unfavorable  conditions. 

Persistent  continuance  of  native  civilization  at  a 
level  which  is  not  especially  low  compared  with 
other  lands  within  the  tropics,  but  is  very  low 
and  unprogressive  compared  with  the  great 
eras  of  the  past. 

__1 _ I _ I _ ! _ I _ _ 1—1 _ lA _ _] _ I _ _ ! _ ! _ ! _ I _ _ ! _ I _ !_ 

B.  C.  A.  D.  100  200  300  400  m  600  700  800  900  1000  1100  1200  1300  1400  1500  1600  1700  1800 


Fig.  72. — Changes  of  Climate  in  California  for  2,000  Years. 

This  figure  is  the  same  as  the  part  of  figure  50  after  100  b.  c.,  but  is  plotted  with  a  three-fold  greater  vertical  scale. 

time,  when  the  ruins  of  Maya  land  have  been  thoroughly  explored  and  excavated,  it  will 
doubtless  be  possible  to  frame  an  exact  chronology,  and  to  determine  the  sequence  of  the 
main  events  in  Maya  history.  The  doing  of  this  will  have  no  bearing  upon  conclusions 
resting  on  such  evidence  as  the  trees  in  California,  but  it  will  prove  an  admirable  test  of 
the  portion  of  our  theory  involving  the  relationship  of  climatic  changes  to  lands  within  the 
tropics,  and  to  the  history  of  civilization  in  that  region. 

Meanwhile  let  us  sum  up  the  net  results  of  our  entire  study  of  climatic  changes,  whether 
in  Arizona,  New  Mexico,  California,  Mexico,  Yucatan,  or  Guatemala.  The  main  signifi¬ 
cance  of  the  whole  matter  lies  in  the  fact  that  from  a  long  and  complex  chain  of  reasoning. 


232 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


beginning  in  Asia  and  extending  to  America,  we  deduce  certain  consequences,  and  on  com¬ 
parison  with  the  actual  facts  we  find  that  on  the  whole  the  facts  and  the  consequences 
essentially  agree.  The  first  step  in  our  reasoning  was  the  simple  theory  that  the  chmate 
of  early  historic  times  was  different  from  that  of  the  present.  The  second  was  the  further 
hypothesis  that  the  change  from  the  past  to  the  present  has  not  been  regular  but  pulsatory. 
This  in  turn  led  to  the  supposition  that  climatic  changes  may  have  been  one  of  the  factors 
which  have  borne  a  part  in  producing  certain  important  historical  results.  These  three 
steps  were  taken  in  Asia  and  the  eastern  countries  of  the  Mediterranean  basin.  The 
next  step  was  to  employ  the  same  methods  of  research  in  similar  regions  of  America,  with 
the  result  that  they  led  to  the  same  general  conclusions.  Having  reached  this  point,  it 
became  necessary  to  drop  the  former  methods  and  make  an  entirely  new  investigation 
absolutely  unconnected  with  the  preceding  steps  and  wholly  independent  of  the  personal 
opinions  of  the  investigator.  This  was  done  by  means  of  the  growth  of  trees.  Its  results 
agreed  with  those  of  the  other  methods  of  investigation  in  indicating  the  pulsatory  nature 
of  climatic  changes.  The  results  also  led  to  two  new  conclusions.  The  first  was  that  in 
continental  regions  lying  in  similar  latitudes  and  in  similar  relation  to  the  sea,  climatic 
pulsations  of  similar  phase  occur  at  the  same  time  both  in  the  eastern  and  in  the  western 
hemispheres.  The  corollary  of  this  is  that  all  parts  of  the  earth  must  be  subject  to  climatic 
changes  at  the  same  time,  although  the  nature  and  degree  of  the  change  may  vary  greatly 
from  place  to  place.  A  second  conclusion  derived  from  the  trees  was  that  climatic  changes 
are  due  primarily  to  a  strengthening  or  weakening  of  the  atmospheric  circulation,  and  that 
their  general  effect  at  one  extreme  is  so  to  weaken  the  movements  of  the  air  that  storms 
are  mild  and  seasonal  variations  slight.  At  the  other  extreme,  on  the  contrary,  storms 
appear  to  be  strong  and  seasonal  variations  to  be  great,  because  the  various  climatic  zones 
of  the  earth  are  moved  far  from  their  ordinary  location,  especially  in  winter.  Finally,  we 
have  taken  all  our  conclusions  as  to  the  nature  of  climatic  changes  and  their  relation  to 
historic  events  and  have  apphed  them  to  a  new  region  in  Central  America.  The  result  is 
a  considerable  degree  of  agreement  between  our  expectations  and  the  facts,  no  matter 
which  of  our  sets  of  dates  is  used.  If  the  interpretation  of  Maya  history  contained  in  our 
table  is  correct,  the  agreement  becomes  truly  remarkable.  In  view  of  the  present  uncer¬ 
tainty  as  to  Maya  chronology,  however,  we  must  once  more  emphasize  the  fact  that  this 
agreement  can  not  be  regarded  as  proving  the  accuracy  of  the  various  steps  leading  to 
our  present  results,  for  there  are  still  many  points  to  be  investigated.  It  seems,  however, 
to  show  clearly  that  even  in  this  last  expansion  of  our  hypothesis  we  find  nothing  con¬ 
trary  to  it.  As  we  go  back  toward  the  earlier  parts  of  the  hypothesis  each  step  becomes 
more  and  more  firmly  established.  Our  main  conclusion  does  not  rest  upon  Maya  history, 
but  upon  the  trees  of  California  and  upon  hundreds  of  pieces  of  evidence  in  the  arid 
Southwest  and  in  Asia.  All  these  seem  strongly  to  indicate  that  the  climate  of  the  past 
was  different  from  that  of  the  present  and  that  the  change  from  that  time  to  this  has  been 
pulsatory. 


CHAPTER  XIX. 


THE  SOLAR  HYPOTHESIS. 

In  the  investigation  of  any  scientific  problem  the  natural  order  of  study  is:  (1)  the 
actual  facts,  past  and  present;  (2)  their  causes;  (3)  their  results;  (4)  the  prediction  of  future 
events.  Thus  far  in  this  volume  we  have  been  endeavoring  to  ascertain  the  actual  facts 
as  to  the  climatic  events  of  the  past  two  or  three  thousand  years.  Here  and  there  we 
have  turned  aside  to  a  discussion  of  results  as  manifested  in  the  topography  of  the  earth, 
its  cover  of  vegetation,  or  its  human  inhabitants,  but  this  has  been  merely  to  aid  us  in 
ascertaining  how  far  the  climate  has  actually  changed.  If  it  be  granted  that  the  main 
conclusions  thus  far  set  forth  are  correct,  the  way  is  open  to  the  other  three  phases  of  the 
subject — the  study  of  causes  and  results,  and  the  prediction  of  the  future.  Each  of  these 
is  so  large  as  to  demand  a  volume  to  itself.  Hence  in  the  following  chapters  I  propose 
merely  to  indicate  briefly  certain  facts  and  relationships  which  appear  to  have  a  bearing 
upon  the  cause  of  climatic  changes.  I  shall  discuss  an  hypothesis  which  presents  a  new 
phase  of  the  old  hypotheses  of  the  relation  of  the  climate  of  the  earth  to  the  activity  of 
the  sun  on  the  one  hand,  and  to  deformation  of  the  earth’s  crust  on  the  other  hand.  I  do 
this  with  full  appreciation  of  the  fact  that  as  yet  the  observational  basis  of  the  hypothesis 
is  small.  I  realize  that  such  an  hypothesis  is  sure  to  be  wrong  in  certain  respects,  and  may 
be  entirely  wrong.  I  do  not  present  it  with  any  expectation  that  it  will  at  once  be  accepted, 
or  that  it  will  supplant  other  theories.  It  is  offered  merely  as  a  first  attempt  to  interpret 
the  theoretical  bearing  of  the  new  facts  set  forth  in  this  book.  Whatever  may  be  the 
ultimate  fate  of  the  hypothesis,  it  may,  perhaps,  at  least  serve  to  stimulate  the  further 
investigation  of  the  phenomena  here  discussed  and  to  promote  the  framing  of  other  and 
better  hypotheses. 

Granting  the  validity  of  the  conclusions  set  forth  in  previous  chapters,  the  period  from 
the  Pleistocene  era  to  the  present  has  been  characterized  by  a  series  of  chmatic  changes  of 
highly  varying  intensity.  At  one  extreme  come  great  changes,  such  as  the  glacial  period, 
lasting  thousands  or  perhaps  hundreds  of  thousands  of  years,  and  forming  some  of  the 
most  noteworthy  phenomena  of  geological  history.  At  the  other  extreme  come  short 
climatic  cycles  of  various  lengths  such  as  2.5,  11,  21,  and  35  years.  Few  students  question 
the  reality  of  either  type  of  change,  although  there  is  much  question  as  to  whether  they  are 
characterized  by  any  permanent  and  regular  periodicity  or  whether  they  occur  merely  at 
irregular  intervals.  Hitherto  these  two  types  have  commonly  been  regarded  as  distinct 
phenomena,  due  in  all  probabihty  to  diverse  causes.  The  glacial  changes  have  been 
supposed  to  be  a  completed  series  of  events,  which  might  recur  again,  but  whose  causes  are 
not  now  operative.  The  minor  cycles  of  the  present  time,  on  the  other  hand,  have  been 
generally  looked  upon  either  as  more  or  less  accidental  phenomena  due  to  fortuitous 
combinations  of  atmospheric  influences,  or  else  as  the  result  of  causes  which  may  or  may 
not  be  connected  with  the  glacial  period,  but  which  at  least  are  separated  from  that  period 
by  a  pronounced  and  unbridged  gap.  This  gap  appears  now  to  be  bridged,  and  in  this  fact 
lies  the  most  important  contribution  of  this  volume  to  our  knowledge  of  the  laws  of  nature. 
Between  the  two  extreme  types  of  climatic  change  typified  by  glacial  periods  and  11-year 
cycles,  there  seem  to  be  two  others  of  intermediate  magnitude.  First,  we  have  the  change 
by  which  the  climate  of  the  world  in  general  appears  now  to  be  different  from  what  it  was 
2,000  to  3,000  years  ago.  This  change  is  perhaps  of  the  same  degree  as  the  changes  of 

233 


234 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


somewhat  earlier  times  which  are  known  as  glacial  stages.  Lastly,  the  fourth  type  of  cli¬ 
matic  change  is  that  which  appears  so  distinctly  in  the  curve  of  the  sequoia.  That  curve 
gives  strong  evidence  of  distinct  climatic  cycles  measured  in  units  of  hundreds  of  years. 
So  far  as  we  can  ascertain,  all  four  of  our  types  of  changes,  from  those  of  the  11-year  period 
up  to  glacial  epochs,  seem  to  be  of  essentially  the  same  nature :  at  one  extreme  they  appear 
to  be  characterized  by  an  expansion  of  the  polar  zone  of  climate  and  a  corresponding  com¬ 
pression  of  the  remaining  zones  toward  the  equator,  and  at  the  other  by  a  contraction  of 
the  polar  zone  and  a  poleward  expansion  of  the  others. 

The  types  of  changes  which  have  just  been  mentioned  do  not  embrace  all  the  climatic 
vicissitudes  to  which  the  earth  is  subject.  Back  of  the  minor  cycles  measured  by  years 
or  decades,  back  of  the  historic  cycles  measured  by  centuries,  back  of  the  climatic  stages 
measured  by  millenniums,  and  back  of  glacial  epochs  measured  by  tens  of  thousands  of 
years,  there  lie  glacial  periods  of  still  vaster  dimensions  composed  of  a  series  of  epochs  and 
measured  in  hundreds  of  thousands  of  years.  They  appear  to  differ  from  one  another 
in  a  way  quite  unlike  that  in  which  one  of  the  smaller  epochs  or  cycles  differs  from  another. 
During  one  glacial  period  the  conditions  favorable  to  glaciation  may  be  localized  in  polar, 
or  at  least  far  northern  latitudes,  as  was  the  case  during  the  Pleistocene  period;  while  during 
another  the  exact  reverse  may  be  true,  and  the  glaciation  may  be  localized  within  from 
20°  to  40°  of  the  equator,  as  happened  in  Permian  times.  This  suggests  that  while  the 
smaller  changes,  from  glacial  epochs  down  to  cycles  of  a  few  years,  may  all  be  of  the  same 
nature,  and  may  be  due  to  the  same  cause,  such  pronounced  phenomena  as  the  Permian 
redistribution  of  the  climatic  zones  as  a  whole  are  probably  due  to  another  cause.  This 
idea,  then,  of  a  twofold  cause  of  the  climatic  instability  of  the  earth  may  serve  as  a  guide 
in  our  future  studies. 

In  attempting  to  ascertain  the  causes  of  any  group  of  facts  two  methods  may  be  pur¬ 
sued.  In  the  first  place,  we  may  search  for  phenomena  whose  effects  are  beyond  the 
range  of  observation,  but  which  the  processes  of  reasoning  lead  us  to  believe  may  be  asso¬ 
ciated  with  the  phenomena  which  we  wish  to  explain.  This  process  has  led  to  two  chief 
climatic  hypotheses:  one  is  Croll’s  theory  of  the  precession  of  the  equinoxes,  and  the 
other  is  the  carbonic-acid  theory,  whose  inception  we  owe  to  Arrhenius,  and  which  has 
been  so  well  elaborated  by  Chamberlain.  In  developing  both  theories  a  long  and  extremely 
complicated  process  of  reasoning  has  been  necessary  in  order  to  reach  a  final  conclu¬ 
sion.  It  has  been  impossible,  even  on  a  small  scale,  to  test  most  of  the  steps  involved  in  the 
reasoning. 

The  other  method  is  the  discovery  of  phenomena  which  can  actually  be  seen  to  vary  in 
harmony  with  the  facts  which  we  desire  to  explain.  This  method  has  also  given  rise  to 
two  climatic  theories.  In  the  first  place,  it  is  evident  to  the  most  unskilled  observer  that 
the  extent,  elevation,  and  relief  of  the  land  are  of  the  highest  importance  in  causing  differ¬ 
ences  in  climate.  From  this  has  arisen  the  theory  that  the  chief  changes  in  the  climate  of 
the  earth  are  due  to  variations  in  the  location,  form,  and  extent  of  the  continents,  accom¬ 
panied  by  corresponding  changes  in  the  circulation  of  the  air  and  of  oceanic  waters.  In 
the  second  place,  no  one  doubts  that  the  amount  of  energy  received  from  the  sun  is  the  fun¬ 
damental  factor  in  determining  the  climate  of  the  different  parts  of  the  world.  If  the 
amount  of  radiation  received  from  the  sun  should  change  appreciably,  the  chmate  of  the  earth 
would  certainly  be  modified.  From  this  has  arisen  the  solar  theory.  The  two  methods 
of  investigation  which  have  just  been  indicated  must  in  practise  be  carried  on  together; 
nevertheless,  there  is  a  distinct  and  important  difference.  A  highly  theoretical  conception, 
such  as  the  precession  of  the  equinoxes  or  the  abstraction  of  carbon  dioxide  from  the 
atmosphere,  is  more  liable  to  error  than  is  an  observational  conception,  such  as  the  climatic 
effect  of  the  altitude  and  form  of  the  lands,  or  the  effect  of  changes  in  solar  radiation  upon 
terrestrial  temperature. 


THE  SOLAR  HYPOTHESIS. 


235 


The  four  theories  which  have  just  been  mentioned,  with  their  appropriate  modifications, 
are  the  only  ones  which  have  hitherto  had  any  permanent  standing  as  attempts  to  explain 
glaciation  or  the  other  climatic  vicissitudes  of  geological  times.  The  precession  theory 
seems  to  have  been  thoroughly  tested  and  found  wanting.  It  demands  a  rigid  periodicity 
which  ought  to  cause  the  recurrence  of  the  same  phenomena  repeatedly  at  precisely  the 
same  intervals.  Possibly  precession  may  account  for  slight  chmatic  variations,  but  the 
larger  changes  fail  entirely  to  meet  its  requirements.  The  three  other  theories — that  is, 
those  of  carbonic  acid,  elevation  of  the  lands,  and  solar  changes — may  be  considered  as 
standing  at  the  present  time  upon  an  equal  footing.  It  is  incumbent  upon  us  now  to  test 
them  in  the  light  of  the  new  knowledge  which  seems  to  have  come  from  the  study  of  the 
climate  of  historic  times. 

The  outstanding  fact  to  which  our  investigations  seem  to  lead  is  that  at  the  present 
time  the  chmate  of  the  world  is  highly  unstable.  Contrary  to  the  old  idea  of  uniformity, 
we  find,  apparently,  that  cycles,  large  and  small,  are  continually  in  progress.  So  far  as 
our  present  knowledge  goes,  it  is  impossible  to  differentiate  between  the  larger  and  the 
smaller  except  in  the  matter  of  size.  If  this  is  so,  it  seems  essential  that  an  acceptable 
theory  should  explain  not  only  the  great  changes  but  the  small  ones.  In  other  words,  if 
we  omit  for  the  moment  the  great  phenomena  of  the  redistribution  of  the  climatic  zones  of 
the  earth  as  a  whole,  and  consider  only  glacial  epochs  and  smaller  phenomena,  the  causes 
of  climatic  variations  must  apparently  be  capable  not  only  of  large,  slow  changes,  but 
also  of  those  which  are  small  and  rapid.  A  cause  must  be  found  to  explain  long  cycles, 
such  as  the  glacial  and  interglacial  epochs  of  the  Pleistocene  period,  and  that  same  cause 
or  some  other  must  also  be  of  such  a  nature  that  in  the  space  of  half  a  century  it  can  produce 
a  change  as  great  as  that  which  apparently  occurred  between  1300  and  1350  a.  d.  At  this 
point  both  the  theory  of  elevation  and  that  of  carbon  dioxide  seem  to  break  down.  It  seems 
as  if  neither  the  altitude  of  the  mountains  and  continents  of  the  world,  nor  yet  the  amount 
of  carbon  dioxide  in  the  air  can,  almost  in  our  own  day,  have  changed  so  quickly  and 
markedly  as  to  cause  an  epoch  such  as  that  which  seems  to  have  culminated  in  the  four¬ 
teenth  century. 

Moreover,  throughout  geological  time  there  is  good  reason  to  think  that  minor  changes 
of  climate  are  of  much  more  frequent  occurrence  than  is  commonly  supposed.  I  have 
discussed  this  matter  in  an  article  upon  ‘‘Characteristics  of  the  Glacial  Period  in  Non- 
glaciated  Regions,’’*  and  shall  not  dwell  on  it  here.  The  work  of  Gilbert  upon  limestones, 
and  the  fuller  work  of  Barrell  upon  sedimentation,  seem  to  indicate  the  constant  succession 
of  minor  climatic  fluctuations  during  a  large  portion  of  geological  time.  These,  too,  must 
be  explained  by  any  complete  climatic  theory. 

Finally,  we  may  add  that  so  far  as  any  absolute  measurements  have  been  made,  we  have 
no  definite  evidence  of  variations  in  chmatic  conditions  corresponding  to  any  observed 
change  in  the  altitude  of  the  earth’s  surface  or  in  the  amount  of  carbon  dioxide  in  the 
air.  Therefore  we  may  say  that  so  far  as  the  small  climatic  changes  are  concerned,  it  is 
hard  to  conceive  of  their  having  arisen  in  accordance  with  either  of  these  two  theories. 
This  by  no  means  must  be  taken  as  implying  that  changes  both  in  the  composition  of  the 
air,  and  far  more  in  the  altitude  and  position  of  the  land,  have  not  had  most  pronounced 
effects.  It  merely  means  that  they  appear  to  be  of  importance  chiefly  in  reference  to 
long-continued,  slow  changes,  but  fail  when  an  attempt  is  made  to  use  them  in  explanation 
of  anything  except  major  phenomena  of  long  endurance. 

At  this  point  we  must  raise  the  query  whether  purely  meteorological  causes  now  in 
operation  may  not  suffice  to  account  for  minor  climatic  changes.  The  varying  conditions 
of  the  seasons,  the  accidental  accumulation  of  masses  of  clouds,  the  fortuitous  convergence 
of  an  unusual  number  of  storms,  the  heating  of  a  portion  of  the  earth’s  surface  by  lava. 


*  Bulletin  of  the  Geological  Society  of  America,  vol.  18,  1907,  pp.  351-388. 


236 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  temporary  filling  of  the  air  with  dust  from  volcanoes,  and  the  cooling  of  parts  of  the 
ocean  by  an  unusual  number  of  icebergs  are  a  few  of  the  many  agencies  which  combine  to 
cause  the  weather  of  one  year  to  differ  from  that  of  another.  It  is  not  only  conceivable, 
but  highly  probable,  that  these  agencies  account  for  a  large  share  of  the  variations  which 
are  visible  within  an  ordinary  human  lifetime.  Many  meteorologists  of  the  liighest 
standing  regard  them  as  a  sufficient  explanation  of  all  changes  since  the  end  of  the  glacial 
period.  These  meteorologists,  however,  assume  a  definite  end  of  the  glacial  period,  and 
their  theory  was  framed  before  the  trees  of  California  had  disclosed  such  strong  evidence  of 
post-glacial  and,  especially,  of  historic  fluctuations. 

Unfortunately  it  is  impossible  to  disprove  or  prove  their  view.  At  the  present  time  we 
are  only  beginning  to  determine  whether  the  difference  between  the  weather  of  one  year  and 
another  is  due  solely  to  meteorological  causes,  such  as  are  mentioned  above,  or  partly  to 
them  and  partly  to  solar  or  other  unknown  agencies.  The  most  that  we  can  do  is  to 
consider  the  probabilities,  and  they  are  bound  to  seem  different  to  different  observers. 
The  earth’s  atmosphere  is  extremely  sensitive  and  mobile.  The  slightest  change  in  temper¬ 
ature,  pressure,  or  other  conditions  sets  it  in  motion.  Because  of  this  mobility,  however, 
there  is  an  equally  prompt  tendency  to  correct  any  departure  from  equilibrium  as  quickly 
as  it  is  formed.  In  summer  the  full  development  of  the  great  areas  of  continental  low 
pressure,  and  of  the  accompanying  monsoons  or  other  in-blowing  winds,  reaches  its  full 
development  only  about  a  month  after  the  sun  reaches  its  most  northern  point.  Therefore 
it  would  seem  as  if  any  accidental  departures  of  the  earth’s  climate  due  to  purely  meteoro¬ 
logical  causes  must  speedily  reach  their  limit,  and  then  disappear  as  the  atmosphere 
attempts  to  regain  its  equilibrium.  So  long  as  we  knew  of  no  climatic  changes  between 
those  of  35-year  cycles  and  those  of  glacial  epochs,  the  purely  meteorological  explanation  of 
present  phenomena  was  commonly  accepted  as  sufficient.  The  changes  indicated  by  the 
California  trees,  however,  seem  to  put  a  strain  on  this  explanation.  They  appear  to  demand 
not  only  that  something  should  have  caused  changes  which  seem  to  be  of  as  great  intensity 
as  those  which  now  differentiate  one  year  from  another,  but  that  the  atmosphere,  in  spite 
of  its  instability,  should  have  been  held  for  a  century  or  two  at  one  or  the  other  of  these 
extremes.  This  may  be  possible,  but  in  many  ways  it  seems  improbable.  Some  other 
cause  seems  needed  thus  to  change  the  condition  of  the  atmosphere  and  then  prevent 
it  from  swinging  back  to  its  old  state  of  equilibrium. 

Coming  now  to  the  sun  as  a  possible  cause  of  climatic  variations  both  large  and  small, 
the  case  is  quite  different.  The  solar  hypothesis  is  not  confronted  by  the  same  difficulties 
as  any  of  the  others.  From  the  work  of  Abbott,  Fowle,  and  others  we  know,  as  a  matter 
of  observation,  that  the  radiation  of  the  sun  varies  to  a  degree  which  is  easily  measurable 
with  the  pjrrheliometer,  but  the  variation  is  quite  irregular  in  duration  and  still  more  so  in 
amplitude,  some  maxima  being  several  times  as  important  as  others.  The  difficulty  with 
the  solar  theory  is  that  it  is  avowedly  indefinite.  The  sun  has  indeed  been  proved  to 
be  a  variable  star,  but  the  observed  variations  are  of  only  slight  magnitude  and  duration. 
We  can,  of  course,  assume  that  in  the  past  it  has  varied  on  a  larger  scale  than  at  present, 
but  no  one  has  yet  been  able  to  point  to  more  than  the  most  shadowy  indications  that 
this  is  the  case.  Moreover,  meteorologists  are  not  as  yet  wholly  agreed  as  to  what  would 
be  the  effect  of  an  increase  in  the  intensity  of  the  sun’s  radiation.  Some  think  that  it  would 
simply  warm  the  earth  and  produce  a  mild  climate,  the  change  being  especially  marked 
far  toward  the  poles.  Others  think  that  its  effect  would  be  felt  chiefly  at  the  equator,  and 
that  thereby  the  circulation  of  the  atmosphere  would  be  so  accelerated  and  cloudiness  in 
non-equatorial  regions  would  be  so  increased  as  to  bring  on  glaciation. 

Without  attempting  to  discuss  this  matter,  let  us  briefly  see  what  ground  there  is  for 
thinking  that  present  changes  in  the  intensity  of  the  sun’s  radiation  are  actually  connected 
with  present  variations  of  climate.  In  the  first  place,  it  is  almost  universally  agreed  that 


THE  SOLAR  HYPOTHESIS. 


237 


there  is  a  very  direct  and  close  connection  between  the  sun-spot  period  and  the  various 
magnetic  phenomena  of  the  earth.  It  is  possible  that  these  magnetic  phenomena  are 
intimately  connected  with  our  cyclonic  storms  or  other  climatic  factors,  but  little  is 
known  about  this  and  we  can  not  here  discuss  it.  As  to  the  general  relation  of  sun-spots 
to  the  common  climatic  elements  of  temperature,  pressure,  winds,  precipitation,  and  the 
like,  the  matter  may  well  be  suromed  up  in  the  words  of  Hann,  the  great  modern  authority 
on  climate:* 

“The  results  of  very  numerous  and  complex  investigations  of  the  connection  of  the  sun-spot 
period  with  variations  of  the  meteorological  elements  have  not  wholly  corresponded  to  expecta¬ 
tions.  The  influence  of  the  sun-spots  on  the  meteorological  elements  has  been  proved  as  com¬ 
paratively  unimportant.  Only  in  the  most  favorable  cases  is  one  in  the  position  to  consider  that 
the  traces  of  a  parallel  course  in  the  progress  of  certain  meteorological  elements  and  in  that  of  the 
sun-spot  frequency  is  proven.  There  can  be  no  thought  of  the  prediction  of  the  course  of  the 
weather  on  the  ground  of  the  sun-spot  cycle.” 

From  this  broad  general  statement  Hann  goes  on  to  show  that  the  amount  of  agreement 
between  sun-spots  and  cHmatic  phenomena  varies  greatly  according  to  the  part  of  the 
earth  and  the  precise  climatic  elements  which  are  investigated.  In  general,  temperature 
is  the  element  which  shows  the  closest  agreement  with  solar  changes,  and  this  applies 
much  more  to  equatorial  than  to  other  regions.  To  quote  Hann  once  more  (p.  356) : 

“For  the  best-grounded  demonstration  of  a  sun-spot  period  in  the  mean  annual  temperature  of 
the  various  regions  of  the  earth  our  thanks  are  due  to  Koppen.f  In  the  tropics  the  parallelism 
of  changes  in  the  mean  annual  temperature  and  of  the  frequency  of  spots  on  the  sun  is  compara¬ 
tively  well  proved,  in  middle  and  higher  latitudes  less  well.  The  mean  amplitude  of  the  changes 
in  the  annual  temperature  from  a  sun-spot  minimum  to  a  maximum  amounts  within  the  tropics  to 
0.75°  C.,  and  beyond  the  tropics  to  0.54°  C.  The  course  of  the  phenomena  within  the  tropics 
appears  from  the  following  numbers,  which  show  the  departure  of  the  yearly  mean  temperature 
from  the  mean  for  a  long  period. 


Table  13. — Sun-spol  Periods  in  the  Yearly  Mean  of  Temperature  loithin  the  Tropics. 


Sun-spot  minimum.  . .' .  -f- 0.33' 

1  year  after  minimum .  -j- 0.15 

2  years  after  minimum .  —  0.04 

3  years  after  minimum .  —  0.21 

4  years  after  minimum .  —  0.28 


Sun-spot  maximum .  —  0.32' 

1  year  after  maximum .  —  0.27 

2  years  after  maximum .  —  0.14 

3  years  after  maximum .  4-  0.08 

4  years  after  maximum .  -f  0.30 

5  years  after  maximum .  -f  0.41 


The  maximum  of  temperature  falls  about  0.9  year  before  the  sun-spot  minimum, 
while  the  minimum  of  temperature  practically  coincides  with  the  maximum  of  the  spots. 

As  to  the  other  climatic  elements,  the  case  is  by  no  means  so  clear,  and  the  results 
sometimes  appear  to  be  contradictory.  The  reader  who  would  carry  the  matter  further 
is  referred  to  the  last  chapter  of  volume  1  of  Haim’s  Klimatologie,  and  to  the  large  number 
of  references  there  cited.  In  general  it  appears  that  the  strongest  evidence  of  a  sun-spot 
cycle  in  climate  is  found  when  a  single  element,  such  as  summer  rains  or  tropical  cyclones, 
to  take  the  two  best  examples,  is  considered  alone,  and  when  it  is  investigated  by  the  use 
of  means  for  a  large  number  of  stations  and  for  long  periods.  When  single  stations  or  single 
sun-spot  cycles  are  considered  there  is  likely  to  be  no  visible  relation  whatever.  In  rainfall, 
as  in  temperature,  there  is  decidedly  more  evidence  of  a  sun-spot  cycle  within  the  tropics 
than  in  other  parts  of  the  world.  One  of  the  most  noticeable  cases  and  one  of  the  few  which 
is  distinct  and  unmistakable  is  found  in  the  number  of  tropical  cyclones  or  hurricanes  both 
in  the  Indian  Ocean  as  investigated  by  Meldrum  and  in  the  Atlantic  according  to  Pocy.J 


*  J.  Hann,  Handbuch  der  Klimatologie,  Stuttgart,  1908,  vol.  1,  pp.  355-356. 
t  W.  Koppen,  Uber  mehrjahrige  Perioden  der  Witterung  in  besondere  iiber  die  11-jahrige 
t  See  Hann,  Klimatologie,  vol.  1,  p.  300. 


Periods  der  Temperature. 


238 


THE  CLIMATIC  FACTOE  AS  ILLUSTRATED  IN  ARID  AMERICA. 


In  both  cases  the  number  and  intensity  of  cyclones  increase  and  decrease  in  harmony 
with  those  of  sun-spots,  the  greatest  number  occurring  at  the  time  of 
maximum  spots,  which  appears  also  to  be  the  time  of  minimum  tem¬ 
perature.  Wolf  has  compared  the  frequency  of  the  cyclones  with  the 
number  of  sun-spots  and  gets  the  interesting  result  seen  in  table  14. 

Here  we  seem  to  have  an  unmistakable  relationship;  but  when 
other  climatic  elements  are  investigated,  for  instance,  thunderstorms, 
hail,  movements  of  glaciers  and  the  like,  and  especially  when  regions 
far  from  the  equator  are  considered,  the  indications  of  a  sun-spot 
cycle  become  so  weak  and  conflicting  that  no  true  causal  connection 
has  yet  been  established.* 

In  view  of  the  importance  and  complexity  of  this  subject  it  seems  advisable  to  test  it 
by  means  of  our  measurements  of  the  growth  of  trees.  This  is  especially  desirable  because, 
although  the  trees  in  some  respects  fail  to  give  a  perfect  record,  their  record  has  the  great 
advantage  of  being  long  and  homogeneous.  Professor  Douglass  has  already  made  a  be¬ 
ginning  in  this  subject.  From  the  trees  of  Arizona  he  has  found  an  apparent  agreement 
between  the  amount  of  growth  and  the  sun-spot  cycle.  The  average  11-year  cycle  for  a 
long  period  seems  to  show  a  double  maximum  in  the  growth  of  trees.  Inasmuch,  however, 
as  an  arbitrary  period  of  11.4  years  was  used  and  no  attention  was  paid  to  the  fact  that  the 
actual  sun-spot  cycle  may  range  from  7  to  16  years,  it  is  questionable  whether  much  rehance 
can  be  placed  on  these  results. 

The  other  method  of  Professor  Douglass,  on  the  contrary,  is  reliable  and  conclusive. 
In  figure  25,  page  120,  he  has  simply  compared  the  growth  of  13  trees  in  Germany  since 
1820  with  the  standard  sun-spot  curve.  The  result  is  striking.  Each  curve  shows  seven 
major  maxima,  and  of  these  seven  all  but  one  occur  at  essentially  the  same  time  in  both 
curves.  In  the  one  exceptional  case,  the  trees  reach  a  maximum  in  1901,  while  the  sun¬ 
spots  do  not  reach  their  highest  point  till  four  years  later.  In  view  of  the  accidents  to  which 
trees  are  liable  and  the  extent  to  which  the  failure  of  the  rains  in  one  or  two  critical  months 
may  check  growth  for  several  years,  one  single  disagreement  out  of  seven  possible  agree¬ 
ments  is  no  more  than  we  should  expect.  The  apparent  relation  between  sun-spots  and 
tree  growth  thus  found  in  Germany  is  especially  significant  because  the  German  curves 
of  temperature  and  rainfall  do  not  agree  so  closely  with  the  sun-spots.  This  seems  to 
indicate  that  when  temperature,  total  rainfall,  and  seasonal  distribution  of  rainfall  are  all 
integrated,  as  they  are  by  the  growth  of  the  trees,  the  sun-spot  cycle  is  more  evident  than 
when  individual  climatic  elements  are  concerned.  This  appears  to  be  the  reverse  of  what 
is  true  in  equatorial  regions.* 

A  test  of  the  trees  of  California  in  this  same  fashion  fails  to  show  any  such  agreement 
with  sun-spots  as  is  found  in  Germany.  In  the  two  curves  of  figure  75  a  resemblance  may 
be  traced  at  certain  points,  but  it  soon  gives  way  to  disagreement  and  appears  to  be  purely 
accidental.  So  far  as  these  particular  curves  are  concerned  there  seems  to  be  no  warrant 
for  believing  in  any  connection  between  solar  changes  and  climate.  The  contrast  in  this 
respect  between  the  German  and  California  curves  is  a  good  illustration  of  the  complexities 
and  apparent  contradictions  of  this  involved  subject.  We  shall  later  inquire  whether 
such  apparent  inconsistency  is  incompatible  with  a  solar  theory  of  climate  or  is  its  ex¬ 
pectable  consequence.  Meanwhile  let  us  investigate  the  same  subject  by  another  method. 

The  method  here  employed  is  simply  to  determine  the  average  rate  of  growth  at  different 
portions  of  the  actual  sun-spot  cycle,  and  see  whether  it  varies  in  harmony  with  the  cycle. 
Beginning  with  1610  a.  d.,  when  the  dates  of  maximum  and  minimum  sun-spots  first  begin 
to  be  known  with  certainty,  each  sun-spot  cycle  has  been  taken  by  itself  and  divided  into 
parts  according  to  table  15. 


Table  14. 


No.  of 
cyclones 
per  year. 

Relative 

sun-spot 

numbers. 

1  and  2 

17 

3 

59 

4 

62 

5 

70 

6  and  7 

80 

8 

88 

*  See  notes  on  pp.  205  and  253. 


THE  SOLAR  HYPOTHESIS. 


239 


Table  15. 

1.  The  year  of  maximum  spots.  6.  One  year  before  minimum. 

2.  The  year  after  maximum.  7.  The  year  of  minimum  spots. 

3.  Two  years  after  maximum.  8.  One  year  after  minimum. 

4.  An  intermediate  period  of  decreasing  9.  An  intermediate  period  of  increasing  spots 

spots  having  an  average  length  of  havinganaveragelengthof  about  1.5  years, 

about  1.5  years.  10.  Two  years  before  maximum. 

5.  Two  years  before  minimum.  11.  One  year  before  maximum. 

In  order  to  have  two  separate  sets  of  data  for  comparison,  the  period  since  1610  is 
divided  into  two  parts,  1610-1754,  and  1755-1900,  each  consisting  of  13  complete  sun-spot 
cycles.  The  two  parts  differ  in  respect  to  the  length  of  time  from  maximum  to  minimum. 
In  the  earlier  period  the  average  lapse  of  time  from  maximum  to  minimum  was  approxi¬ 
mately  the  same  as  from  minimum  back  to  maximum,  or  about  5.5  years  in  each  case. 


17.50  1760  1770  1780  1790  1800  1810  1820  1&30  1840  18,50  18G0  1870  1880  1890  1900 


In  the  later  period  the  time  from  maximum  to  minimum  was  not  far  from  6.5  years,  while 
that  from  minimum  back  to  maximum  was  4.5.  Hence  in  the  first  period  it  was  necessary 
to  omit  No.  3  in  table  15,  and  in  the  second  period  to  omit  No.  10,  thus  in  each 
case  leaving  the  sun-spot  cycle  divided  into  ten  parts,  eight  of  which  have  a  length  of  a 
year,  and  two  of  1.5  j'^ears.  For  each  of  these  ten  parts  I  have  computed  the  average 
growth  of  eleven  sequoia  trees,  the  only  ones  whose  yearly  growth  it  has  yet  been  possible 
to  measure  back  to  1610  a.  d.  with  sufficient  accuracy.  The  results  are  shown  in  figure  76. 

In  order  to  test  the  matter  in  a  somewhat  similar  way  in  Europe  I  have  computed  the 
average  price  of  wheat  in  England  according  to  the  tables  of  Thorold  Rogers,  using  the 
same  ten  divisions  of  each  sun-spot  cycle.  The  use  of  these  tables  was  suggested  by 
A.  H.  Swinton,  Esq.,  of  Totnes,  England,  who  has  devoted  much  time  to  a  careful  study 
of  the  relation  of  sun-spots  and  weather.  During  the  peiicd  ficm  1610  to  1754  England 
produced  her  own  food  supply,  economic  conditions  did  not  change  greatly,  and  there  were 
no  protracted  or  highly  devastating  wars.  Accordingly  the  main  factor  in  determining 
variations  in  the  price  of  wheat  was  the  amount  actually  raised  in  the  country  itself;  and 
that,  of  course,  was  dependent  chiefly  upon  variations  in  the  weather  from  year  to  year, 
dry  years  being  in  general  favorable  so  that  prices  were  low,  and  wet  years  unfavorable  so 
that  prices  were  high.  During  the  later  period,  1755  to  1900,  the  Napoleonic  wars,  the 
growth  of  manufactures,  the  importation  of  food  from  America,  and  changes  in  the  tariff 
have  completely  altered  the  conditions  of  British  agriculture,  so  that  the  price  of  wheat  no 
longer  depends  upon  the  amount  raised  locally.  Hence  it  is  not  possible  to  use  this  later 
period. 

Thus  in  figure  76  we  have  three  curves,  H  and  I  on  the  left  for  the  period  from  1610 
to  1754,  and  I'  on  the  right  for  1754-1900.  Above  these  the  sun-spot  curves,  G  and  G', 
have  been  placed,  G  being  merely  an  estimated  curve,  since  exact  data  are  not  available, 
while  G^  is  the  mean  of  the  actual  observations  as  given  by  Wolf.  In  using  data  derived 
from  sources  such  as  the  growth  of  trees  and  the  price  of  wheat  it  is  obvious  that  there  is  a 
large  opportunity  for  error,  partly  from  mistakes  in  actual  observation,  but  chiefly  because 


240 


THE  CLIMATIC  FACTOK  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  the  many  non-climatic  accidents  to  which  vegetation  and  prices  are  both  liable.  This 
error  can  not  be  wholly  ehminated.  Its  effect,  however,  is  reduced  by  the  fact  that  each 
point  in  the  unsmoothed  curves,  the  dotted  lines  in  figure  76,  represents  the  average 
condition  at  that  particular  phase  of  13  cycles.  Moreover,  the  values  for  each  cycle  are 
in  turn  the  average  of  a  considerable  number  of  records  in  the  case  of  the  price  of  wheat 
and  of  18  measurements  along  the  radii  of  11  trees  in  the  other  case.  In  order  still  further 
to  eliminate  accidents  I  have  drawn  the  solid  lines  which  represent  the  results  of  smoothing 
by  the  use  of  3-year  means.  For  instance,  the  year  before  minimum,  the  year  of  minimum. 


1610-1754. 


Sunspot  Curve 


Price  of  wheat  in 
England  1610-1764. 


Growth  of  13  Sequoia 
trees  in  California 
1610-1754. 


1755-1899. 


ZYrs. 

lYear 

lYear 

I^Yrs.of 

lYear 

lYear 

2Yrs. 

I^Yrs.of 

before 

before 

Min. 

after 

increasing 

before 

Max. 

after 

after 

decreasing 

Min. 

Min. 

Min. 

Spots 

Max. 

Max. 

Max. 

Spots 

Sunspot  Curve 
1755-1901 


Growth  of  13  Sequoia 
trees  in  California 
1755-1899 


Volcanic  eruptions 


Fig.  76. — The  Sun-spot  Cycle  and  Terrestrial  Phenomena. 


and  the  year  after  minimum  have  been  averaged,  and  the  result  plotted  in  the  minimum 
year.  Thus  in  general  each  point  in  the  smoothed  curve  of  tree  growth  is  the  average  of 
18  by  13  by  3,  or  702  measurements.  With  so  large  a  basis  of  facts  it  seems  probable  that 
accidental  errors  have  been  largely  eliminated.  The  remaining  departures  of  the  curves 
from  straight  fines  would  seem  to  indicate  some  permanently  variable  factor  which  varies 
in  harmony  with  the  sun-spot  cycles  and  for  that  reason  will  not  disappear  even  when  a 
large  body  of  data  is  averaged.  Aside  from  climate  there  appears  to  be  no  known  factor 
which  could  vary  in  such  a  way  as  to  have  the  same  periodicity  as  sun-spots  and  yet  cause 
the  rate  of  growth  of  vegetation  to  fluctuate. 

Taking  the  solid  fines  G,  H,  I,  and  I'  and  the  dotted  fine  G'  in  figure  76  we  see  that  they 
are  in  substantial  agreement.  The  curve  of  prices  is  at  a  minimum  at  the  time  of  the  sun¬ 
spot  minimum,  and  reaches  a  maximum  a  year  before  that  of  the  solar  curve.  Its  highest 
point  is  nearly  25  per  cent  higher  than  the  lowest.  The  curve  of  the  sequoias  for  the 
earlier  period  is  at  a  minimum  a  year  before  the  sun-spots  and  at  a  maximum  a  year  later 
than  the  spots.  The  difference  in  this  case  is  only  4  per  cent,  but  the  change  from  minimum 
to  maximum,  even  in  the  unsmoothed  curve,  is  so  regular  that  it  seems  as  if  it  must  be  due 
to  a  genuine  difference  in  the  amount  of  rain  at  different  portions  of  the  sun-spot  cycle. 
The  fact  that  the  sequoia  curve  for  the  second  period,  I',  presents  almost  the  same  appear¬ 
ance  lends  color  to  this  conclusion,  more  especially  as  the  difference  between  maximum 
and  minimum  is  here  about  10  per  cent.  Such  an  agreement  among  phenomena  occurring 
in  two  distinct  periods  in  regions  far  remote  from  one  another  is  important,  since  it  adds 
another  to  the  many  fines  of  evidence  which  suggest,  though  they  do  not  prove,  a  connection 
between  the  solar  cycle  and  terrestrial  climate.  It  also  points  to  the  probability  that  in 
extra-tropical  regions  climatic  records  extending  over  a  long  period  may  disclose  a  cycle 
which  is  completely  masked  by  the  minor  variations  which  take  place  from  year  to  year. 

Without  attempting  to  press  this  point  further,  let  us  see  exactly  what  our  curves  appear 
to  indicate.  The  curve  of  the  price  of  wheat  has  its  maximum  a  year  before  the  solar 
maximum.  Inasmuch  as  the  price  of  grain  responds  quickly  to  variations  in  the  crop,  it 


THE  SOLAR  HYPOTHESIS. 


241 


seems  fair  to  suppose  that  the  maximum  price  would,  on  an  average,  be  reached  within  a 
year  after  the  minimum  crop  was  harvested.  The  worst  crops  in  England  are  those  of  the 
wettest  years  when  the  ground  is  w'aterlogged  and  there  is  scanty  sunshine.  Hence  we 
may  infer  that  in  the  period  from  1610  to  1754  a.  d.  the  maximum  rainfall  in  England 
occurred  on  an  average  one  or  two  years  before  the  time  of  maximum  sun-spots.  In  studying 
the  sequoias  of  California  we  found  that  the  maximum  growth  comes  on  an  average  about 
two  years  after  the  maximum  rainfall.  In  the  curves  before  us  the  maximum  of  the 
unsmoothed  curve  for  the  fii’st  period  comes  two  years  after  the  sun-spot  maximum,  and 
that  of  the  smoothed  curve  one  year.  In  the  later  period  the  same  relation  is  observed. 
Subtracting  two  years  from  the  time  of  maximum  growth,  we  find  that  the  probable  time 
of  maximum  rainfall  in  California  is  a  year  or  less  before  the  sun-spot  maximum,  a  result 
which  agrees  closely  with  that  obtained  in  England  and  suggests  that  these  two  regions  in 
the  western  parts  of  two  great  continents  fare  somewhat  similarly,  so  far  at  least  as  winter 
rains  are  concerned.  This  agrees  with  the  conclusion  derived  from  our  curves  of  changes 
of  climate  in  America  and  Asia  for  the  past  2,000  or  3,000  years.  When  minor  fluctuations 
are  eliminated,  times  of  heavy  precipitation  in  the  corresponding  parts  of  the  eastern 
hemisphere  and  of  America  seem  approximately  to  coincide. 

The  chief  objections  to  the  theory  of  an  11-year  climatic  cycle  due  to  sun-spots  are 
two.  In  the  first  place,  while  it  must  apparently  be  granted  that  the  earth’s  temperature 
actually  varies  in  harmony  with  the  spots  of  the  sun,  the  variation  is  so  slight  that  many 
of  the  highest  authorities  consider  it  too  small  to  have  an  appreciable  effect.  In  the 
second  place,  while  the  various  meteorological  elements,  especially  rainfall  and  tropical 
cyclones,  show  some  indications  of  a  cycle  corresponding  with  that  of  the  sun,  the  evidence 
of  this  is  thus  far  largely  confined  to  the  region  within  the  tropics.  Even  there,  and  still 
more  in  other  places,  curious  contradictions  are  noticed.  Let  us  examine  each  of  these 
objections  in  detail. 

Our  consideration  of  the  objection  that  changes  in  the  amount  of  heat  received  from 
the  sun  are  insufficient  to  cause  appreciable  meteorological  phenomena  may  well  center 
on  an  article  by  Newcomb.*  This  article  is  so  important  that  its  appearance,  together 
with  that  of  a  similar  article  by  Bigelow,  led  Hann  to  add  an  appendix  to  the  first  volume 
of  his  “Klimatologie”  after  the  main  volume  was  finished. 

Newcomb’s  study  of  the  relation  of  the  temperature  of  the  sun  to  that  of  the  earth  is 
the  most  comprehensive  and  accurate  that  has  yet  been  made.  His  conclusions  are  so 
careful  and  conservative  that  they  can  scarcely  be  doubted  so  far  as  they  are  based  directly 
upon  statistics.  He  expresses  himself  thus  (p.  379) : 

“A  study  of  the  annual  departures  [from  mean  temperature]  over  many  regions  of  the  globe 
in  equatorial  and  middle  latitudes  shows  consistently  a  fluctuation  corresponding  with  that  of 
the  solar  spots.  The  maximum  fluctuation  in  the  general  average  is  0.13°  C.  on  each  side  of  the 
mean  for  the  tropical  regions.  [The  maximum  temperature  coming  at  times  of  minimum  sun¬ 
spots.]  The  entire  amplitude  of  the  change  is  therefore  0.26°  C.  [0.47°  F.],  or  somewhat  less 
than  half  a  degree  of  the  Fahrenheit  scale.” 

On  an  earher  page  (341)  he  says: 

“Although  the  reality  of  this  11-year  fluctuation  [both  solar  and  terrestrial]  seems  to  be 
placed  beyond  serious  doubt,  the  amplitude  being  several  times  its  probable  error,^  its  amount  is 
too  small  to  produce  any  important  direct  effect  upon  meteorological  phenomena.’ 

Again,  on  page  384,  he  puts  in  italics  the  last  part  of  the  following  quotation: 

“It  follows  as  the  final  result  of  the  present  investigation  that  all  the  ordinary  'phenomena 
of  temperature,  rainfall,  and  winds  are  due  to  purely  terrestrial  causes,  and  that  no  changes  occur  in 
the  sun’s  radiation  which  have  any  influence  upon  them”  _  _ 

*  A  Search  for  Fluctuations  in  the  Sun’s  Thermal  Radiation  through  their  Influence  on  Terrestrial  Temperature, 

by  Simon  Newcomb.  Trans.  Am.  Phil.  Soc.  U.  S.,  vol.  21,  v,  1908. 

17 


242 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


While  Newcomb’s  conclusion  as  to  the  change  of  temperature  between  the  times  of 
maximum  and  minimum  sun-spots  rests  upon  unassailable  evidence,  his  last  conclusion  as 
to  the  relation  of  the  changes  to  meteorological  phenomena  is  based  purely  on  inference 
and  is  open  to  question.  He  has  failed  to  consider  the  effect  which  even  a  shght  change  of 
temperature  may  have  upon  meteorological  conditions  provided  it  be  permanent.  In  his 
1 1-year  cycle  the  range  of  temperature  is  0.26°  C.  In  order  to  estimate  the  true  importance 
of  such  a  variation,  it  is  necessary  to  consider  what  would  be  the  result  if  the  temperature 
no  longer  fluctuated  back  and  forth  between  the  two  extremes  every  eleven  years,  but 
remained  constant  at  one  extreme  for  a  few  centuries  and  then  at  the  other  for  a  corre¬ 
sponding  length  of  time. 

In  order  to  explain  the  glacial  period,  geologists  and  students  of  “paleo-meteorology” 
postulate  a  change  of  the  mean  temperature  of  the  earth’s  atmosphere  many  times  larger 
than  Newcomb’s  change  in  the  11 -year  cycle,  but  not  of  a  different  order  of  magnitude. 
Penck,  the  leading  German  student  of  glaciation,  beheves  that  a  permanent  change  of 
5°  C.  is  sufficient  to  account  for  the  difference  between  the  conditions  of  the  glacial  period 
and  those  of  to-day.  According  to  Ekholm,  a  lowering  of  the  mean  annual  temperature 
to  the  extent  of  from  7°  to  9°  C.  would  cause  the  snow-line  of  the  earth  as  a  whole  to  descend 
3,300  feet,  and  would  lead  to  a  revival  of  the  glacial  period.  Bonney  thinks  that  during 
the  glacial  period  the  temperature  of  England  was  about  20°  F.  lower  than  it  now  is,  and 
the  mean  temperature  of  the  earth’s  atmosphere  as  a  whole  was  from  15°  to  20°  F.  lower 
than  at  present.  Bruckner  states  that  a  lowering  of  the  earth’s  temperature  to  the  extent 
of  3°  or  4°  C.  would  probably  suffice  to  account  for  the  phenomena  of  the  glacial  period. 
He  considers  that  the  change  in  temperature  would  be  relatively  shght  in  equatorial 
regions  and  great  in  polar  regions.  Finally,  David,  from  a  study  of  glaciation  in  Australia 
and  other  less  familiar  parts  of  the  world,  arrives  at  the  conclusion  that  in  order  to  explain 
the  phenomena  of  the  last  great  advance  of  the  ice  it  must  be  assumed  that  the  temperature 
of  that  time  was  lower  than  that  of  the  present  by  “probably  not  less  than  5°  C.” 

The  average  value  of  the  decrease  in  temperature  necessary  to  produce  a  glacial  period, 
according  to  the  statements  of  the  five  authorities  cited  above,  amounts  to  from  5°  to  6°  C. 
That  is,  they  conclude  that  if  the  mean  temperatm’e  of  the  earth  were  to  fall  5°  or  6°  C., 
and  were  to  remain  thus  low  for  a  sufficient  length  of  time,  meteorological  conditions  would 
be  so  altered  that  a  large  part  of  North  America  would  be  shrouded  with  ice  down  to 
about  the  fortieth  degree  of  latitude,  and  Europe  would  suffer  a  corresponding  glaciation. 
If  a  change  of  from  5°  to  6°  C.  would  produce  such  a  result,  it  seems  reasonable  to  suppose 
that  the  change  of  0.26°  C.  which  Newcomb  has  determined  in  the  eleven-year  sun-spot 
cycle  would  produce  a  corresponding  result  on  a  smaller  scale,  provided  the  duration  of 
the  period  of  low  temperature  were  long  enough.  To  take  a  specific  case  for  illustration, 
the  Rhone  glacier  is  now  barely  6  miles  long;  the  foot  of  the  ice  stands  at  a  height  of  5,780 
feet  above  sea-level  and  the  surface  of  the  ice  at  its  origin  is  10,200  feet  above  the  sea. 
During  the  period  of  maximum  glaciation  the  glacier  was  240  miles  longer  than  it  now  is; 
its  foot  stood  about  4,700  feet  lower  than  is  now  the  case,  and  its  surface  near  the  origin 
was  1,400  feet  above  the  present  surface. 

For  the  sake  of  conservatism,  let  it  be  assumed  that  the  change  of  temperature  which, 
together  with  corresponding  changes  in  winds  and  precipitation,  was  necessary  to  cause 
the  Rhone  glacier  to  assume  its  former  great  dimensions  was  13°  C.,  which  is  greater  than 
the  maximum  figure  given  above  (Bonney’s,  20°  F.,  or  11.1°  C.),  and  more  than  twice 
the  mean  of  the  five  authorities  cited.  Then  a  change  of  0.26°  C.  would  be  one-fiftieth 
of  the  change  necessary  to  cause  the  Rhone  glacier  to  assume  the  dimensions  which  it  had 
during  the  glacial  period.  It  seems  fair  to  assume  that  the  results  of  a  small  change  of 
chmate  would  be  approximately  proportional  to  those  of  a  larger  change.  If  this  is  so, 
the  difference  of  0.26°  C.,  which  Newcomb  finds  between  the  mean  temperature  of  periods 


THE  SOLAR  HYPOTHESIS. 


243 


of  minimum  sun-spots  and  those  of  maximum  sun-spots,  would  cause  pronounced  changes 
in  the  Rhone  glacier,  provided  the  low  temperature  lasted  long  enough  to  allow  of  the 
abundant  accumulation  of  snow.  In  that  case,  if  the  form  of  its  valley  were  favorable, 
the  Rhone  glacier  might  become  5  miles  longer  than  it  now  is;  or,  if  the  gradient  of  the 
valley  bottom  be  assumed  as  uniform,  the  ice  might  descend  90  feet  below  its  present  level ; 
or  the  glacier  might  increase  28  feet  in  thickness.  The  exact  nature  of  the  change  in  the 
glacier  and  its  exact  dimensions  would  depend  upon  the  topography  of  the  Rhone  Valley 
and  upon  the  relation  of  precipitation  to  temperature,  winds,  and  other  meteorological 
phenomena,  but  the  figures  which  have  just  been  given  show  the  order  of  magnitude  of  the 
results  which  might  be  expected  from  a  lowering  of  the  mean  annual  temperature  of  the 
earth  to  the  extent  of  0.26°  C.,  provided  always  that  the  change  were  permanent  rather 
than  temporary.  A  change  of  temperature  capable  of  producing  such  results,  or  even 
results  half  as  great,  would  scarcely  seem  to  be  too  small  to  produce  "any  important  effect 
upon  meteorological  phenomena.”  The  truth  of  Newcomb’s  conclusions  appears  to  be  at 
least  an  open  question. 

Let  us  turn  now  to  the  other  great  objection  to  the  theory  of  an  eleven-year  climatic 
cycle  due  to  the  sun:  Regions  within  the  tropics  may  show  fairly  strong  indications  of 
such  a  cycle,  but  even  there  a  certain  number  of  apparent  contradictions  are  found,  while 
as  higher  latitudes  are  gained  the  indications  appear  to  become  much  less  distinct  and 
more  contradictory.  Is  such  a  state  of  affairs  consistent  with  the  theory  of  the  climatic 
influence  of  sun-spots?  At  first  sight  one  is  inclined  to  answer  with  a  categorical  negative, 
but  the  recent  meteorological  investigations  of  Arctowski  oblige  us  to  reconsider  the 
matter.  By  a  patient  sifting  of  a  vast  mass  of  figures  he  has  shown  that  both  in  Europe  and 
America  there  appear  to  be  areas  of  abnormal  pressure,  temperature,  rainfall,  and  the  like, 
which  persist  for  several  years  and  move  irregularly  backward  and  forward.*  His  con¬ 
clusions  are  based  partly  on  direct  meteorological  records  and  partly  upon  statistics  of  the 
growth  of  wheat  or  corn.  His  method  can  best  be  described  by  means  of  specific  examples. 
Taking  as  a  standard  the  mean  temperature  of  the  various  portions  of  the  United  States  or 
Europe,  Arctowski  has  computed  the  departure  of  each  station  from  the  normal.  At  first 
he  did  this  by  years,  but  in  his  later  work,  which  is  not  yet  pubfished,  by  months.  The 
results  are  striking.  He  finds  that  the  regions  where  the  mean  temperature  for  the  given 
period  is  above  or  below  the  normal  are  not  distributed  irregularly  but  with  much  system. 
He  does  not  find  one  region  showing  excess  while  its  immediate  neighbor  shows  deficiency, 
and  the  one  beyond  that  again  excess.  On  the  contrary,  the  excess  of  temperature  is 
greatest  at  one  particular  point;  from  there  it  decreases  gradually  until  the  area  of  normal 
temperature  is  reached,  beyond  which  the  excess  gives  place  to  deficiency,  which  in  turn 
centers  around  a  definite  spot.  The  degree  of  regularity  is  such  that  lines  of  equal  excess 
or  deficiency  can  be  drawn  in  the  same  fashion  as  isotherms.  These  present  almost  the 
appearance  of  the  isobars  of  a  barometric  map,  as  is  illustrated  in  figures  77  to  80.  These 
particular  maps  represent  the  corn  crop,  but  maps  of  temperature,  pressure,  or  the  growth 
of  other  crops  would  have  the  same  general  appearance,  although  the  areas  of  excess  or 
deficiency  would  be  different  in  each  case.  The  areas  which  are  above  the  normal  in 
temperature  have  been  termed  "pleions”  by  Arctowski,  and  those  below  normal  "anti- 
pleions,”  those  above  or  below  the  normal  in  pressure  are  called  areas  of  "hyper-pressure” 
and  of  "hypo-pressure,”  while  places  having  an  excess  or  deficiency  of  crops  are  desig¬ 
nated  "fats”  and  "leans.”  For  the  sake  of  convenience,  however,  I  shall  depart  somewhat 
from  his  usage,  and  shall  speak  of  all  areas  of  excess  as  pleions  and  all  areas  of  deficiency 
as  anti-pleions.  Thus  we  may  have  a  pleion  of  temperature,  crops,  or  pressure,  and  the 
three  may  be  quite  unrelated  to  one  another.  In  the  year  1901  it  will  be  seen  that  so 

*  Bulletin  American  Geographical  Society,  vol.  42,  1910,  pp.  270  and  481;  vol.  44,  1912,  pp.  598  and  745,  \ol. 

45,  1913,  pp.  117-131.  L’enchatnement  des  variations  clunatiques,  Bruxelles,  19Uy. 


244 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA 


Fig.  77. — The  Corn  Crop  of  the  United  States,  1901,  a  “Lean”  Year,  after  Arctowski. 


Fig.  78.— The  Corn  Crop  of  the  United  States,  1906,  a  “Fat”  Year,  after  Arctowski. 


THE  SOLAR  HYPOTHESIS. 


245 


Fig.  79. — The  Corn  Crop  of  the  United  States,  1908,  after  Arctowski. 


Fig.  80. — The  Corn  Crop  of  the  United  States,  1909,  after  Arctowski. 


246 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


far  as  the  production  of  corn  was  concerned,  extremely  anti-pleionic  or  “lean”  conditions 
prevailed  over  most  of  the  United  States,  which  means  that  there  was  an  especial  deficiency 
in  the  rains  of  June  and  July.  In  1906,  on  the  contrary,  only  one  small  area  was  lean,  and 
even  there  the  deficiency  was  less  than  2.5  bushels  per  acre.  Throughout  all  the  rest  of  the 
country  “fat”  conditions  prevailed — that  is,  the  crop  was  better  than  the  average. 

Figures  79  and  80,  for  the  years  1908  and  1909,  illustrate  an  interesting  feature  of  the 
pleions  and  anti-pleions  of  all  sorts  of  meteorological  phenomena,  namely,  their  persistence 
from  year  to  year  in  spite  of  certain  changes  in  form  and  location.  The  large  anti-pleion 
in  the  center  of  the  United  States  in  1908  has  contracted  in  its  east-and-west  dimensions 
and  has  moved  south  in  1909,  but  it  is  clearly  recognizable.  In  similar  fashion  the  minute 
anti-pleion  over  Delaware  in  1908  has  expanded  over  New  Jersey,  Pennsylvania,  Maryland, 
and  part  of  Virginia  in  1909. 

This  emphasizes  a  most  characteristic  and  important  feature  of  the  pleions  and  anti- 
pleions — that  is,  their  movability.  By  means  of  a  series  of  monthly  charts  based  on  over¬ 
lapping  means  for  12  months  and  thus  eliminating  all  variations  due  merely  to  the  succession 
of  the  seasons,  Arctowski  has  discovered  that  a  given  pleion  may  last  for  many  years,  during 
which  its  center  moves  back  and  forth  in  irregular  curves  whose  north-and-south  component 
apparently  exceeds  the  east-and-west.  Sometimes  they  grow  weak  and  tend  to  divide 
into  two  or  more  sections,  and  practically  disappear,  while  again  they  strengthen  and 
gather  into  strongly  localized  areas  of  pronounced  intensity.  Just  where  they  originate  or 
how  they  disappear  is  not  yet  clear,  but  apparently  they  do  not  often  pass  from  the  sea  to  the 
land.  This  much,  however,  is  certain:  they  are  a  pronounced  feature  of  continental  and 
perhaps  of  oceanic  climates,  and  deserve  most  careful  study,  since  in  them  may  lie  the  key 
to  the  prediction  of  the  character  of  a  season — months  or  even  a  year  or  two  beforehand. 

For  our  present  purpose  another  phase 
of  Arctowski’ s  study  of  pleions  and  anti- 
pleions  is  particularly  important.  In  his 
article  on  Arequipa*  he  shows  that  the  44 
values  of  the  “solar  constant”  as  measured 
by  Abbott  and  Fowle  between  October  9, 

1902,  and  May  14,  1907,  agree  in  general 
with  the  departures  of  the  mean  monthly 
temperature  from  the  normal  at  Arequipa. 

This  appears  in  figure  81,  where  the  upper 
curve  shows  the  changes  of  the  solar  con¬ 
stant  in  calories  and  the  lower  the  depar¬ 
tures  of  atmospheric  temperature  at  Are¬ 
quipa.  To  quote  Arctowski : 

“It  is  obvious  that  the  number  of  observa¬ 
tions  of  the  ‘solar  constant’  is  insufficient  to 
show  all  the  details  of  the  variation.  More¬ 
over,  some  measurements  may  have  been  taken 
precisely  on  exceptional  days,  giving  values  which  would  not  have  very  greatly  influenced  results 
of  continuous  records.  Special  meteorological  conditions  may  also  have  influenced  the  obtained 
figures.  But,  taking  the  uncertainty  of  the  results  into  account,  it  is  astonishing  to  see  such  a 
close  agreement  between  the  two  curves.  *  *  *  Supposing  that  the  fluctuations  of  the ‘solar 
constant’  and  those  of  the  monthly  means  of  temperature  observed  at  Arequipa  coincide,  which 
is  far  from  being  certain,  as  the  diagram  shows  that  a  delay  is  more  probable,  I  compared  the 
Mount  Wilson  measurements  with  the  Arequipa  monthly  departures  of  temperature.  To  have 

*  The  Solar  Constant  and  the  Variations  of  Atmospheric  Temperature  at  Arequipa  and  some  other  stations. 

Bulletin  American  Geographical  Society,  vol.  44,  1912,  pp.  598-606. 


THE  SOLAR  HYPOTHESIS. 


247 


comparable  figures  I  made  monthly  means  of  the  121  observations  taken  at  Mount  Wilson  from 
June  to  October  1905  and  from  May  to  October  1906.  The  differences  between  these  figures, 
compared  with  the  differences  between  the  departures  of  the  corresponding  months,  led  me  to 
the  supposition  that  a  departure  in  temperature  of  1°  F.,  in  a  monthly  mean  observed  at  Arequipa, 
is  due  to  a  departure  of  about  0.015  of  the  'solar  constant’  from  its  normal  value.  If  this  is  the 
case,  we  may  admit  that  a  comparably  [comparatively?]  small  lowering  of  the  ‘solar  constant,’ 
if  permanent,  could  produce  climatical  changes  such  as  those  which  have  really  existed  during  the 
Pleistocene  ice  age.  The  required  diminution  would  indeed  fall  entirely  within  the  range  of  the 
momentary  changes  observed  at  Mount  Wilson,  the  extreme  values  being  1.93  and  2.14  calories. 
But  it  is  useless  to  make  more  far-reaching  speculations,  the  acquired  facts  being  sufficient  to 
show  the  cause  of  the  formation  of  pleions  in  tropical  regions.” 


1900  1901  1902  1902  1904  1905  1906  1907  1908  1909  1910 


Fig.  82. — Monthly  Departures  of  Temperature  in  South  Equatorial 
Regions,  showing  Agreement,  after  Arctowski. 


Arctowski’s  conclusion  that  the  pleions  of  equatorial  regions  are  really  due  to  changes 
in  the  solar  constant  receives  support  from  the  fact  that  other  places  in  the  same  zone  of 
climate  are  characterized  by  similar  variations.  Thus  figure  82  shows  the  smoothed 
curves  of  monthly  departures  for  four  stations  having  a  latitude  of  from  16°  to  20°  S., 
but  distributed  well  around  the  world  in  longitude.  The  agreement  of  the  four  curves  is 
unmistakable.  If  seasonal  variations  played  a  part  in  the  matter  this  agreement  would 
possess  no  significance,  but  such  is  by  no  means  the  case.  Each  point  on  the  curves  repre¬ 
sents  the  mean  of  12  months,  the  middle  point  of  a  year  representing  the  mean  of  one 
January  to  the  following  December,  the  next  point  February  to  the  succeeding  January, 
then  March  to  February,  and  so  forth. 

The  next  diagram,  figure  83,  represents  the  similarly  smoothed  mean  departures  of 
four  stations  ranging  across  the  torrid  zone  from  Arequipa,  latitude  16°  23'  S.,  through 
Batavia,  6°  10'  S.,  and  Colombo,  6°  59'  N.,  to  Bombay,  18°  54'  N.  The  upper  three  curves 
agree  fairly  well.  Batavia,  which  has  a  typically  equatorial  chmate  of  the  simplest  sort, 
has  a  curve  like  that  of  Arequipa  except  that  it  is  less  sinuous  and  the  maxima  of  1900  and 
the  end  of  1907  almost  flatten  out.  Colombo  in  Ceylon  has  a  climate  similar  to  that  of 
Batavia  except  that  it  is  not  quite  so  simple,  being  influenced  somewhat  by  monsoon  winds 
due  to  the  great  size  of  Asia.  Its  curve,  however,  resembles  that  of  Batavia,  except  that 
it  is  decidedly  more  irregular  and  lags  a  little  behind  that  of  Arequipa.  Bombajq  the  most 
northern  of  our  stations,  is  quite  different  from  the  rest.  Probably  this  is  because  its  climate 
is  highly  complex  by  reason  of  the  strong  contrast  between  the  northeast  monsoons  or  trades 
of  the  dry  winter  and  the  southwest  or  true  monsoons  of  the  rainy  summer.  Its  curve,  then, 
as  might  be  expected,  shows  the  same  periodicity  as  that  of  the  other  stations,  but  with  a  lag 
of  a  year  or  more  in  the  main  crests  and  with  the  curious  addition  of  minor  crests  corre¬ 
sponding  to  the  Arequipa  crests,  as  occurs  in  the  years  1905  and  1907.  It  is  as  if  the 


248 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


departures  from  the  mean  temperature  at  Bombay  were  due  to  the  same  cause  as  those  at 
Arequipa  and  the  other  stations,  but  the  direct  effects  of  this  appear  to  produce  only  minor 
maxima,  such  as  those  of  1905  and  1907,  while  the  greatest  effects  are  produced  after  a  delay 
of  a  year  or  so,  during  which  the  excess  of  temperature  accumulated  farther  south  is  perhaps 
brought  north  by  ocean  currents  driven  by  the  monsoons. 

The  supposition  of  a  delay  of  this  sort  is  strengthened  by  the  curves  presented  in  figure 
84.  Here  Arctowski  has  compared  the  departures  from  mean  temperature  at  Arequipa  with 
those  of  a  series  of  stations  from  Key  West  along  the  Atlantic  coast  to  Eastport.  Here,  just 
as  in  the  other  case,  agreement  gives  place  to  disagreement  when  a  pronounced  disturbing 
factor  is  introduced.  The  curves  for  Key  West,  Tampa,  and  Savannah  agree  quite  closely 
with  that  of  Arequipa  from  1900  to  1905,  when  the  maxima  come  in  winter,  but  there¬ 
after  they  disagree  markedly  when  the  Arequipa  maximum  comes  in  summer.  In  this 
case  the  factor  is  not  the  monsoons,  but  may  be  the  concentration  of  warm  equatorial 


1900  1901  1902  1903  1904  1905  1906  1907  1908  1909  1910 


Fig.  83. — Monthly  Departures  of  Temperature  in  North  and  South  Equatorial 
Regions,  Showing  Disagreement,  after  Arctowski. 


waters  to  form  the  Gulf  Stream.  North  of  the  West  Indies  conditions  once  more  change, 
and  New  York  agrees  with  Arequipa,  but  with  a  delay  of  a  few  months.  This  may  mean 
one  of  two  things:  either  the  temperature  of  New  York  responds  directly  to  the  same 
stimulus  as  Arequipa,  perhaps  because  of  its  dependence  upon  a  great  continent  easily 
warmed,  or  else  (which  seems  much  less  likely)  it  responds  indirectly  and  with  a  delay 
approximately  equal  to  the  average  lapse  of  time  from  one  Arequipa  minimum  to  the  next. 
This  might  happen  if  the  variations  of  the  New  York  temperature  were  largely  dependent 
on  the  Gulf  Stream,  but  as  a  matter  of  fact  they  depend  more  largely  upon  great  interior 
regions  whence  come  our  westerly  winds. 

The  sun’s  radiation  is  distributed  equally  to  all  parts  of  the  earth,  but  the  inclination 
of  the  axis,  the  variations  of  the  seasons,  the  distribution  of  land  and  sea,  the  presence  of 
clouds,  the  movements  of  winds  and  ocean  currents,  and  a  host  of  other  accidental  cir¬ 
cumstances  cause  it  to  be  concentrated  now  in  one  place  and  now  in  another.  In  equatorial 
regions  and  in  the  North  Atlantic  Ocean  there  is  a  permanent  concentration,  so  that  the 
temperature  is  relatively  high.  Over  the  continents  a  temporary  concentration  occurs  in 
summer.  If  the  sun’s  total  gift  of  heat  to  the  earth  is  thus  irregularly  distributed,  the 
effect  of  any  variations  from  the  average  must  be  distributed  in  the  same  irregular  fashion, 
being  concentrated  at  the  equator  or  over  the  North  Atlantic  at  all  times,  over  the  con¬ 
tinents  in  summer,  and  in  other  places  according  to  local  circumstances.  A  result  of  this 
concentration  is  perhaps  seen  in  the  middle  of  1901.  At  Arequipa  (for  some  reason  which 


THE  SOLAR  HYPOTHESIS. 


249 


19n0  1901  1902  1903  1904  1905  1906  1907  1908  1909  1910 


we  will  temporarily  assume  to  be  the  variation  of  solar  radiation)  a  slight  rise  of  tempera¬ 
ture  took  place  at  this  time;  north  of  the  equator  this  rise  causes  a  hump  in  the  curves 
for  Key  West,  Tampa,  and  Savannah;  at  Raleigh  it  produces  a  distinct  though  unim¬ 
portant  maximum;  at  New  York  this  maximum  has  become  important,  although  not  of 
the  first  rank,  while  still  farther  to  the  north  and  east  it  becomes  a  primary  phenomenon. 

In  similar  fashion  other  pecuharities  can  be  traced  throughout  all  the  curves.  Take 
the  month  of  March  1906,  for  example.  The  Arequipa  curve  shows  merely  an  insig¬ 
nificant  little  hump;  in  the  Key  West  and  Tampa  curves  this  begins  to  become  impor¬ 
tant  :  in  those  of  Savannah,  Raleigh,  and 
Washington  it  becomes  of  primary  impor¬ 
tance,  while  farther  to  the  northeast  it 
once  more  drops  into  insignificance.  Almost 
any  of  the  other  peculiar  features  of  the 
curves  can  similarly  be  seen  to  show  a 
maximum  development  in  certain  latitudes, 
and  from  there  to  decrease  in  intensity  but 
by  no  means  to  disappear.  If  Arctowski’s 
pleions  are  due  to  variations  in  the  sun’s 
radiation,  we  should  expect  exactly  this — 
that  is,  we  should  expect  to  find  that  they 
would  vary  in  intensity  and  in  their  place 
of  origin,  according  to  the  season  and  other 
circumstances  which  determine  where  the 
sun’s  heat  is  most  concentrated.  Thus  it 
may  happen  that  at  one  time  a  wave  of 
excessive  temperature  originates  in  the  hot 
center  of  the  United  States  during  summer, 
let  us  say,  and  produces  its  maximum  effect 
there  only  a  short  time  after  its  origin, 
while  under  other  circumstances  the  origin 
of  the  wave  may  be  in  the  North  Atlantic 
Ocean,  or  south  of  the  equator,  and  its  effect 
may  reach  the  central  United  States  only  in 
an  attenuated  form  after  much  delay. 

Taken  as  a  whole  the  work  of  Arctowski 
seems  to  indicate  three  things ; 

(1)  In  regions  having  a  pure  equatorial 
climate  little  influenced  by  outside  causes, 
variations  of  terrestrial  temperature  show 
a  general  agreement  with  variations  in  the 
solar  constant. 

(2)  Regions  having  a  more  complex  climate,  with  temperatures  dependent  upon  the 

movement  of  large  bodies  of  air  and  water,  show  the  same  type  of  variations,  but  with 
pronounced  irregularities  and  with  a  certain  degree  of  delay;  that  these  variations  of 
temperature  are  the  same  as  Arctowski’s  pleions  and  anti-pleions  can  scarcely  be  questioned, 
the  pleions  and  anti-pleions  of  temperature  appear  to  influence  winds  and  storms,  and  thus 
to  determine  the  amount  of  rainfall,  but  this  result  is  not  necessarily  direct  nor  immediate, 
so  that  there  is  opportunity  for  the  merging  of  one  pleion  with  another  or  for  the  develop¬ 
ment  of  other  u’regularities.  ,  r  i-f 

(3)  The  response  of  vegetation  (and  especiallj'^  of  great  trees  like  those  of  California) 
to  the  variations  in  rainfall  involves  still  other  delays  and  opportunities  for  the  obliteration 


250 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  some  maxima  and  the  accentuation  of  others.  Hence,  if  it  be  true  that  solar  changes 
influence  terrestrial  climate,  we  should  expect  that  in  some  places  the  results  would  be 
immediately  and  clearly  visible,  while  elsewhere  they  would  be  masked  in  such  a  way  as 
to  be  invisible  when  comparison  is  made  between  such  phenomena  as  the  sun-spot  curve 
and  the  curve  of  growth  of  great  trees  like  the  sequoias;  yet  even  here,  if  we  examine  long 
periods  and  obtain  averages  of  many  sun-spot  cycles,  we  should  expect  to  find  some  trace 
of  the  influence  of  the  sun.  And  this  is  exactly  what  we  find;  the  trees  of  Germany  (which 
depend  upon  summer  rains  and  have  only  a  slight  conservation  factor)  vary  their  rate  of 
growth  in  close  harmony  with  the  sun-spot  cycle.  The  sequoias  of  California,  on  the 
contrary,  with  their  winter  precipitation  and  large  conservation  factor,  show  in  their 
growth  the  same  general  periodicity  as  the  sun-spots,  but  individual  maxima  or  minima 
by  no  means  agree  with  those  of  the  sun.  Yet  when  the  growth  of  a  century  or  two  is 
considered  the  trees  are  found  on  an  average  to  grow  relatively  fast  when  the  sun-spots 
are  at  a  maximum,  and  slowly  when  they  are  at  a  minimum. 

The  work  of  Arctowski  does  not  exhaust  the  recent  contributions  to  our  knowledge  of 
ways  in  which  the  effect  of  solar  radiation  upon  terrestrial  climate  may  be  modified. 
While  the  proof  of  this  volume  was  being  read  there  came  to  hand  a  paper  by  Abbott  and 
Fowle,*  two  students  of  solar  physics  who  have  done  much  to  demonstrate  the  existence 
of  a  relationship  between  solar  radiation  and  terrestrial  temperature.  They  now  show  that 
during  the  summer  of  1912  volcanic  dust  from  the  volcano  of  Katmai  in  Alaska  seems  to 
have  filled  the  upper  air  to  such  an  extent  that  it  decreased  the  amount  of  solar  radiation 
received  on  the  earth’s  surface  by  about  10  per  cent  of  the  normal  solar  constant.  More¬ 
over,  they  present  a  certain  amount  of  evidence  indicating  that  other  volcanic  eruptions, 
such  as  that  of  Krakatoa  in  1883  and  Bandai-San  in  Japan  in  1888,  have  produced  similar 
effects.  The  most  important  part  of  their  paper,  however,  is  a  diagram  which  is  not 
reproduced,  but  which  in  all  essentials  is  almost  identical  with  figure  85.  This  shows  a 
previously  published  set  of  curves  comprising  the  sun-spot  curve  from  1880  to  1909,  the 
curve  of  departures  from  the  mean  temperature  at  15  stations  in  the  United  States, 
and  a  similar  curve  of  departures  for  the  whole  world.  These  three  curves,  to  quote 
Abbott  and  Fowle,  show  “a  considerable  degree  of  correspondence — yet  it  is  not  hard  to 
see  that  there  is  also  much  discordance.”  They  are  among  the  pieces  of  evidence  referred 
to  on  a  previous  page  which  on  the  whole  lead  to  the  conviction  that  terrestrial  tempera¬ 
ture  varies  in  accordance  with  fluctuations  in  the  spots  of  the  sun.  Our  authors  now  add 
to  their  previous  diagram  a  curve  showing  recorded  variations  in  the  intensity  of  the  sun’s 
direct  radiation  as  measured  at  the  earth’s  surface  and  as  modified  by  such  terrestrial 
phenomena  as  the  dust  of  volcanic  eruptions.  They  then  combine  this  curve  with  that  of 
the  sun-spots  in  such  a  way  that  the  sun-spot  curve  still  predominates,  but  is  considerably 
modified.  The  correspondence  between  this  modified  curve  and  the  temperature  curves, 
particularly  that  of  the  United  States,  is,  as  they  truly  say,  “most  striking.” 

After  the  preceding  paragraph  was  written  and  when  the  page-proof  of  this  volume 
was  being  indexed,  still  another  important  article  on  the  same  subject  came  to  hand.f 
In  this  Professor  W.  J.  Humphreys  follows  a  line  of  reasoning  almost  identical  with  that  of 
Abbott  and  Fowle,  and  comes  to  the  same  conclusion,  but  carries  it  farther.  In  an  un¬ 
published  manuscript,  which  he  has  kindly  placed  at  my  disposal,  he  applies  his  results 
to  the  climatic  changes  of  geological  times,  and  emphasizes  the  importance  of  changes  in 
continental  form,  oceanic  currents,  and  related  phenomena  in  a  way  which  differs  little 
from  that  employed  by  Professor  Schuchert  and  myself  in  the  remaining  portions  of  this 
volume.  The  main  points  of  difference  between  his  ideas  and  those  here  presented  are 
that  in  the  first  place  he  regards  variations  in  solar  activity  as  of  negligible  importance 

*  Volcanoes  and  Climate,  by  C.  G.  Abbott  and  F.  E.  Fowle,  Smithsonian  Mis.  Coll.,  GO,  No.  29.  Washington,  1913. 
t  W.  J.  Humphreys,  "Volcanic  Dust  and  Other  Factors  in  the  Production  of  Climatic  Changes,  and  their  Possible 

Relation  to  Ice  Ages.”  Bulletin  of  the  Mount  Weather  Observatory,  vol.  6,  part  1,  August  20,  1913,  pp.  1-26. 


THE  SOLAR  HYPOTHESIS. 


251 


so  far  as  our  present  knowledge  is  concerned,  while  in  the  second  place  he  strongly  empha¬ 
sizes  the  importance  of  volcanic  dust,  a  factor  whose  importance  has  not  hitherto  been 
appreciated.  Humphreys’s  main  conclusion  may  be  summed  up  in  his  own  words: 

“Variations  in  the  average  temperature  of  the  atmosphere  depend  jointly  upon  volcanic  erup¬ 
tions  through  the  action  of  dust  on  radiation,  *  *  *  and  upon  sun-spot  numbers,  through,  pre¬ 
sumably,  some  intermediate  action  they  have  upon  the  atmosphere  (Bulletin  Mount  Weather 
Observatory,  vol.  6,  p.  25).  *  *  *  It  appears,  from  various  considerations,  that,  with  a  constant 
or  nearly  constant  output  of  solar  energy,  the  earth  itself  possesses  the  inherent  ability  of  profoundly 
modifying  its  own  climates,  whether  only  local  or  world-wide.  Thus,  as  the  laws  of  radiation 
indicate  must  be  true,  and  as  observations,  at  least  back  to  1750,  the  date  of  the  earliest  reliable 
records,  show,  the  temperature  of  the  lower  atmosphere  is  distinctly  influenced  by  the  amount  of 
volcanic  dust  in  the  upper  atmosphere,  in  the  sense  that  when  this  amount  is  great  the  average 
temperature  at  the  surface  of  the  earth  is  abnormally  low,  and  when  the  dust  is  absent  this  tem¬ 
perature  is  comparatively  high.  Hence,  as  there  appear  to  have  been  several  periods  of  great 
volcanic  activity  in  the  past  with  intervening  periods  of  quiescence,  it  is  inferred  that  volcanic  dust 
in  the  upper  atmosphere  was  at  least  an  important  factor  in  some,  if  not  all,  of  the  great  and  uni¬ 
versal  climatic  changes  that  have  left  their  records  in  abandoned  beaches  and  forsaken  moraines.” 

The  work  of  Abbott,  Fowle,  and  Humphreys  seems  so  convincing  that  we  can  scarcely 
doubt  that  the  presence  of  volcanic  dust,  temporarily  at  least,  is  an  important  factor  in 
determining  climatic  conditions.  The  degree  of  importance,  however,  is  open  to  question. 
This  can  be  tested  by  two  methods,  first  by  seeing  how  far  present  conditions  of  terrestrial 
temperature  and  climate  actually  vary  in  harmony  with  the  amount  of  volcanic  dust, 
and  second  by  ascertaining  to  what  extent  volcanic  activity  and  glacial  periods  have  been 
coincident  during  geological  times.  The  test  according  to  the  first  method  is  easily 
made  by  studying  figure  85,  which  is  a  reproduction  of  the  last  part  of  Humphreys’s  main 
diagram  and  is  to  all  intents  the  same  as  the  diagram  of  Abbott  and  Fowle.  According 
to  these  diagrams,  volcanic  dust  does  not  appear  to  be  the  main  factor  in  determining 
climatic  variations,  although  it  seems  to  be  an  important  contributing  factor.  In  figure  85, 
the  upper  curve  P  represents  variations  in  the  intensity  of  solar  radiation  as  measured 
by  the  pyroheliometer.  The  curve  dips  suddenly  in  1884  just  after  the  eruption  of 
Krakatoa,  in  1902-3  when  Pel6,  Santa  Maria,  and  Colima  were  in  eruption,  and  in  1912 
when  Katmai  in  Alaska  belched  out  dust.  Another  dip  occurs  in  1890-91  and  may  perhaps 
be  due  to  Bandai-San  in  Japan  and  Bogoslof  in  Alaska,  but  this  is  by  no  means  clear. 
The  second  curve  {S)  is  that  of  sun-spots,  reversed  in  order  to  bring  the  maxima  at  low 
levels  and  the  minima  at  high.  The  third  curve  represents  a  combination  of  P  and  S. 
The  lowest  curve  is  the  average  departure  from  mean  temperature  at  17  American  stations 
and  13  in  other  parts  of  the  world.  It  seems  to  be  representative  of  the  world  as  a  whole. 
Manifestly  the  temperature  curve  is  closely  similar  to  the  curve  formed  by  combining  the 
pyroheliometer  and  sun-spot  curves  and  its  relationship  to  that  can  scarcely  be  doubted. 
When  the  temperature  curve  is  compared  with  P  and  S  individually,  however,  one  sees  at 
once  that  it  bears  a  somewhat  pronounced  resemblance  to  S  but  very  httle  to  P .  The 
logical  conclusion  would  therefore  seem  to  be  that  variations  in  the  sun  are  the  main 
factor  in  modifying  terrestrial  temperature,  but  their  effect  may  be  much  modified  by 
the  presence  of  volcanic  dust  in  the  atmosphere. 

My  own  investigations  seem  to  confirm  this  conclusion.  Before  the  appearance  of 
the  articles  by  Abbott,  Fowle,  and  Humphreys,  I  had  tested  the  relation  of  tree  growth  and 
volcanic  eruptions  according  to  the  method  employed  with  sun-spots  and  the  growth  of 
trees  as  explained  on  pages  238  and  239.  That  is,  taking  all  the  known  volcanic  eruptions 
since  1755  a.  d.,  I  gave  each  one  a  weight  of  1,  2,  or  3,  according  to  its  severity,  and  then 
computed  the  intensity  of  volcanic  activity  at  different  portions  of  the  sun-spot  cycle. 
The  results  appear  as  curve  J  in  figure  76  on  page  240,  but  all  mention  of  the  mattei 


252 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


5— com'«-'OoNcoa>5_'Mn^ovONco(r>2?  —  = 


Katmai 


was  omitted  from  the  text  until  the  present  time  because  of  the  doubt  attaching  to  the 
whole  subject.  The  curve,  however,  was  allowed  to  remain.  When  the  smoothed  vol¬ 
canic  curve  is  compared  with  the  smoothed  curve  of  tree  growth,  /'  in  figure  76,  a  certain 
amount  of  resemblance  is  seen,  but  this  breaks  down  at  the  right-hand  end  of  the  curves, 
and  is  by  no  means  so  pronounced  as  the  similarity  between  the  curves  of  tree  growth 

and  sun-spots.  Hence  it  would  seem  that 

O  ^ 

this  method,  as  well  as  that  of  Abbott, 
Fowle,  and  Humphreys,  leads  to  the  con¬ 
clusion  that  although  volcanic  dust  may 
at  certain  times  have  an  important  influ¬ 
ence  upon  terrestrial  temperature,  and  thus 
upon  other  climatic  elements,  the  effect  of 
solar  radiation  is  much  more  important. 
The  second  method  of  testing  the  control  of 
climate  by  volcanic  dust  has  been  used  by 
Professor  Schuchert,  in  Part  II  of  this 
volume.  It  is  so  purely  geological  that  I 
shall  leave  it  for  the  next  chapter.  Mean¬ 
while,  so  far  as  present  conditions  are  con¬ 
cerned,  we  seem  to  be  led  to  the  conclusion 
that  although  the  solar  hypothesis  can  not 
be  regarded  as  proved,  and  although  other 
factors,  such  as  volcanic  dust,  have  played 
an  important  part,  changes  of  the  sun  seem, 
on  the  whole,  to  explain  the  known  facts 
better  than  any  other  hypothesis  yet  sug¬ 
gested.  Present  changes  in  the  intensity 
of  the  sun’s  radiation  not  only  seem  to  be 
of  sufficient  amplitude  to  produce  distinct  climatic  effects,  but  the  time  of  their  occur¬ 
rence  seems  to  be  in  harmony  with  the  observed  variations  of  chmate.  The  reason  this 
has  not  hitherto  been  realized  seems  to  be  partly  that  due  allowance  has  not  been  made 
for  the  fact  that  the  effects  of  the  sun’s  heat  are  concentrated  on  certain  portions  of  the 
earth’s  surface  and  can  not  reach  other  places  and  influence  the  other  meteorological 
elements  without  the  lapse  of  an  appreciable  and  variable  amount  of  time.  An  equally 
important  or  even  stronger  reason  seems  to  be  that  the  function  of  volcanic  dust  in  mod¬ 
ifying  terrestrial  temperature  has  only  recently  been  discovered. 

Turning  now  from  the  minor  climatic  fluctuations  of  the  present  time  to  the  fluctuations 
of  all  sizes  from  glacial  epochs  downward,  let  us  sum  up  our  conclusions: 

It  appears,  in  the  first  place,  that  of  the  well-established  hypotheses  of  chmatic  changes 
only  the  solar  and  volcanic  hypotheses  invoke  causes  capable  of  varying  and  actually  known 
to  vary  with  sufficient  rapidity  to  cause  changes  of  climate  such  as  the  trees  of  California 
appear  to  give  evidence  of  during  the  past  three  thousand  years. 

In  the  second  place,  numerous  authorities,  including  the  majority  of  meteorologists, 
believe  in  the  existence  of  a  climatic  cycle  related  to  the  sun-spot  cycle,  and  the  trees  of 
Germany  and  California,  as  well  as  the  prices  of  wheat  in  England,  add  their  quota  of 
evidence  to  this  same  effect. 

Thirdly,  the  sun’s  radiation  is  universally  acknowledged  as  the  controlhng  factor  of 
terrestrial  climate.  It  has  been  proved  to  vary  from  one  extreme  of  the  sun-spot  cycle 
to  another,  but  the  amount  of  variation  is  held  by  so  high  an  authority  as  Newcomb  to  be 
too  slight  to  cause  appreciable  meteorological  phenomena.  Nevertheless,  a  comparison  of 
his  results  with  the  conclusions  of  students  of  the  glacial  period  suggests  that  the  solar  vari- 


Krakatoa  Tarawera  Bogo&lof 
Bandaisan  Awoe 


Pel^  Colima 
Santa  Mana 


Fig.  85. — The  Relation  of  Volcanoes,  Sun-spots,  and 
Terrestrial  Temperature,  after  Humphreys. 


THE  SOLAR  HYPOTHESIS. 


253 


ation  in  the  eleven-year  cycle  is  quite  sufficient  to  cause  appreciable  meteorological  results, 
though  the  effect  of  either  extreme  is  largely  neutralized  by  a  speedy  change  to  the  other. 

Finally,  the  great  objection  to  the  solar  hypothesis  has  been  that  while  abundant 
indications  of  an  eleven-year  climatic  cycle  have  been  found,  it  has  rarely  been  possible 
to  point  to  specific  terrestrial  phenomena  as  the  result  of  specific  solar  phenomena.  The 
work  of  Arctowski,  Abbott,  Fowle,  and  Humphreys  supplies  this  deficiency  and  suggests 
that  the  constantly  varying  conditions  of  the  earth’s  surface  may  induce  a  given  solar 
variation  to  produce  its  chief  effect  sometimes  at  one  point  and  sometimes  at  another, 
or  that  the  obstructive  action  of  volcanic  dust  may  shut  out  solar  radiation  for  a  time  in 
certain  areas  or  even  in  all  parts  of  the  world.  Moreover,  effects  which  appear  to  be  due 
to  solar  variation  seem  to  be  transmitted  in  the  form  of  waves  or  by  means  of  winds  and 
currents  and  thus  may  not  reach  a  given  point  until  after  a  delay  of  more  or  less  duration. 
All  things  considered,  the  solar  hypothesis  seems  to  fit  the  facts  better  than  any  other, 
so  far  as  the  changes  of  climate  indicated  by  our  tree  curves  are  concerned.  The  theories 
of  precession,  elevation,  and  carbon  dioxide  seem  too  slow  and  ponderous  to  account  for 
changes  which  last  only  1,000  years  or  less  and  are  geologically  very  rapid  and  small. 
On  the  other  hand,  from  the  standpoint  of  man’s  history^  a  change  whose  duration  is  1,000 
years  is  relatively  slow  and  important,  and  is  probably  too  large  to  be  due  to  purely 
terrestrial  causes,  such  as  accidental  perturbations  in  the  atmosphere.  Volcanic  activity, 
on  the  other  hand,  may  vary  either  in  long  or  short  intervals,  and  thus  meets  all  the 
requirements  in  this  respect,  but  the  actual  curves  which  record  its  variations  fail  to 
show  any  marked  agreement  with  the  general  course  of  chmatic  phenomena,  although 
they  show  marked  agreement  at  selected  periods.  The  sun,  however,  seems  to  meet 
all  the  requirements.  It  is  known  to  vary  on  a  small  scale,  it  is  certainly  adequate  to 
produce  the  observed  effects,  and  there  is  no  reason  why  its  variations  should  not  in  the 
past  have  been  on  a  larger  scale  than  at  present.  Whether  the  sun  could  vary  sufficiently 
to  produce  all  the  climatic  variations  of  geological  times,  and  whether  it  was  the  only  cause 
of  those  variations,  is  another  question,  which  will  be  discussed  in  the  next  chapter. 


NOTE. 

The  completion  of  the  new  work  of  Professor  Kullmer  mentioned  on  p.  205  furnishes  strong 
confirmation  of  the  conclusions  reached  in  this  chapter.  In  an  address  before  the  Association 
of  American  Geographers  at  Princeton,  January  1,  1914,  he  has  shown  that  in  the  belt  of  the 
northern  United  States  and  southern  Canada  where  storms  on  the  average  are  most  numerous, 
the  number  of  storms  varies  almost  directly  in  harmony  with  the  number  of  sun-spots,  just  as  is 
the  case  with  tropical  hurricanes.  In  other  areas,  however,  the  reverse  appears  to  be  true,  and 
there  is  a  decrease  in  storminess.  The  general  conclusion  seems  to  be  that  when  sun-spots  are 
few  in  number  cyclonic  storms  move  in  a  great  variety  of  tracks,  but  when  spots  are  numerous 
the  storms  tend  to  confine  themselves  to  a  few  well-defined  tracks,  so  that  storminess  is  more  or 
less  restricted  to  certain  areas  within  which  it  is  highly  concentrated.  Under  such  conditions  it 
is  possible  for  pronounced  climatic  changes  to  occur  with  only  a  minimum  variation  in  the  mean 

temperature  of  the  earth  as  a  whole.  .  <•  u  ■  u- 

Kullmer’s  work  has  led  the  present  author  radically  to  revise  the  conclusions  set  forth  in  this 
chapter.  While  the  general  conclusions  are  not  changed  they  are  greatly  amplified,  and  thus 
lead  to  a  wholly  new  form  of  the  solar  hypothesis,  and  to  a  new  conception  of  such  phenomena  as 
the  formation  of  loess  during  glacial  periods,  or  the  localization  of  glaciation  during  the  Permian 
era.  These  new  conclusions  are  fully  set  forth  in  a  paper  entitled  “  The  Cyclonic  Solar  Hypothesis 
of  Climatic  Changes,”  which  will  probably  appear  in  the  Bulletin  of  the  Geological  Society  of 
America  during  1914. 


CHAPTER  XX. 

CRUSTAL  DEFORMATION  AS  THE  CAUSE  OF  CLIMATIC  CHANGES. 


We  have  been  led  to  the  conclusion  that  among  the  four  chief  hypotheses  of  climatic 
change  only  the  solar  hypothesis  seems  competent  to  explain  the  pulsations,  large  and 
small,  which  have  taken  place  from  the  glacial  period  to  the  present  time.  In  the  case  of 
the  greatest  of  all  climatic  changes,  however,  this  theory  in  its  turn  appears  to  be  inade¬ 
quate.  So  far  as  we  can  see,  no  possible  change  in  the  sun’s  radiation,  or  in  volcanic 
activity,  could  cause  such  a  complete  redistribution  of  the  earth’s  climatic  zones  as  we  find  in 
the  Permian  and  other  eras.  It  might  cause  the  zones  to  be  pushed  greatly  toward  or  away 
from  the  equator,  to  contract  or  expand,  and  to  vary  considerably  in  temperature,  but  it 
could  scarcely  cause  them  to  be  reversed  in  such  a  way  as  to  make  the  polar  regions  as  warm 
as  the  equator.  The  carbonic  acid  theory,  in  spite  of  ingenious  attempts  to  indicate  a 
possible  method  to  the  contrary,  also  seems  to  many  geologists  inadequate  to  produce  any 
such  result,  and  even  the  framers  of  the  theory  admit  that  this  is  the  case.  They  fall  back 
upon  the  well-established  theory  of  changes  in  the  form  and  altitude  of  the  lands,  and 
consequent  alterations  of  oceanic  and  atmospheric  circulation.  Other  students  suggest 
that  the  pecuharities  of  Permian  times  may  have  been  due  to  a  shifting  of  the  earth’s  axis 
of  rotation,  but  astronomers  and  physicists  find  so  many  objections  to  this  hypothesis  that 
we  can  not  wisely  lay  much  stress  on  it. 

Before  discussing  this  matter  any  further  and  suggesting  a  possible  relationship  between 
solar  changes  and  crustal  deformation,  it  will  be  well  to  review  the  climatic  history  of 
geological  times  as  a  whole.  In  such  a  review  there  is  much  opportunity  for  the  exercise 
of  personal  judgment.  In  this  respect  it  is  harder  to  deal  with  geological  times  than  with 
the  historic  period  wherein  we  can  rely  upon  actual  records,  such  as  those  of  the  growth 
of  trees.  In  order  to  obtain  as  unbiased  a  statement  of  the  facts  as  possible,  I  have  asked 
Professor  Charles  Schuchert  to  contribute  a  discussion  of  geological  climates.  This  dis¬ 
cussion  is  probably  the  fullest  and  most  authoritative  that  has  yet  appeared.  It  is  printed 
as  the  concluding  portion  of  this  volume.  Professor  Schuchert  wrote  his  paper  without 
regard  to  the  theories  discussed  in  this  book,  and  without  definite  knowledge  of  them. 
His  statements  may  be  taken  as  representing  the  mature  conclusions  of  the  most  advanced 
students  of  geology  and  paleontology.  Where  matters  are  doubtful,  he  has  clearly  stated 
the  doubt,  but  so  far  as  our  present  problem  is  concerned  the  points  wherein  geologists 
disagree  are  not  of  vital  importance.  The  student  who  would  understand  the  matter 
thoroughly  is  referred  to  Professor  Schuchert’s  paper.  In  the  following  paragraphs  I  shall 
recapitulate  some  of  his  chief  conclusions,  and  shall  see  how  they  bear  on  those  already 
reached  in  this  volume. 

The  study  of  paleometeorology,  as  set  forth  by  Professor  Schuchert,  leads  to  the 
conclusion  that  the  earth  has  passed  through  a  considerable  number  of  great  cHmatic 
changes,  either  glacial  periods  or  other  periods  marked  by  a  pronounced  decrease  in  temper¬ 
ature  or  increase  in  aridity.  The  best-known  is  of  course  the  Pleistocene  glacial  period. 
Equally  important,  though  more  remote  and  less  well  known  in  detail,  is  the  glacial  period 
of  early  Permic  time.  Both  glaciations  were  world-wide  in  their  effect,  and  were  char¬ 
acterized  by  a  change  in  temperature  suflficient  to  occasion  vast  accumulations  of  snow 
and  ice,  not  only  in  polar  regions  and  at  high  altitudes,  but  even  more  markedly  at  low 
levels  in  middle  or  almost  equatorial  latitudes  where  the  glaciation  in  many  places  reached 

255 


256 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


the  sea.  The  continental  glaciers  of  Pleistocene  time  were  located  mainly  in  the  northern 
portion  of  the  northern  hemisphere,  while  those  of  Permic  time  reached  their  greatest 
extent  20°  to  40°  south  of  the  present  equator,  and  to  a  less  degree  between  20°  and  40° 
north  of  the  equator.  The  Pleistocene  glaciation  was  general  in  the  arctic  region,  while 
that  of  Permic  times  almost  certainly  did  not  prevail  in  that  region.  Both  periods  of 
glaciation  apparently  consisted  of  a  series  of  glacial  and  interglacial  epochs,  as  is  clearly 
brought  out  by  Professor  Schuchert.  The  evidence  consists  in  part  of  an  abundant 
interglacial  flora  which  is  found  in  many  cases  between  distinctly  glacial  deposits  during 
Pleistocene  glacial  times,  and  of  coal  beds  which,  in  Australia,  are  interstratified  with 
glacial  till  of  Permic  age.  These  two  things  are  typical  of  a  great  body  of  evidence  which 
indicates  that  glaciation  did  not  last  uninterruptedly  throughout  either  period.  The 
climate  apparently  fluctuated  back  and  forth  between  conditions  which  promoted  glaciation 
and  those  which  caused  the  ice  to  retire. 

A  rapidly  growing  body  of  evidence  indicates  that,  in  addition  to  the  well-known  Pleisto¬ 
cene  and  Permic  periods  of  glaciation,  there  were  at  least  two  and  probably  three  other 
periods  not  merely  of  local  but  widespread  glacial  climates.  All  of  these  were  geologically 
very  ancient  and  were  earlier  than  the  Paleozoic  era.  The  last  of  them  was  at  or  near  the 
close  of  Proterozoic  time;  another  was  still  earlier,  although  its  position  is  somewhat 
doubtful;  the  third  was  at  the  very  beginning  of  Proterozoic  time  and  almost  at  the  begin¬ 
ning  of  earth  history  as  known  to  geologists.  One  at  least  of  these  periods  appears  to  have 


Aridity 

"N  Maximum  aridity 

3 

Mini 

num  ari 

dity 

Tropical  temperature 

4 

Tom 

perature 

curve 

^5 

\ 

n 

^ - 

Temperate 

/ 

6 

\ 

•  ; A 

7 

— 

Frigid  temperature 

8 

Mountains 

2  3  4  5 

6 

7 

8 

9 

1( 

11 

12 

,1 

13 

nil 

14  1 

5 

t. 

16 

17 

18 

19 

20  21 

♦—41 

22 

HI 

f  ^  ^ 

- ^ 

Ti 

— i 

nes  of  n 

- ^ 

lountai 

- % — 

1  making 

r — 

- ^ 

- ^ 

- ^ 

Geologic  time 

Proterozoic 

Lower 

Cambric 

Middle 

Cambric 

Upper 

Cambric 

Lower 

Ordovicic 

1 

Middle 

Ordovicic 

Upper 

Ordovicic 

Siluric 

Devon  ic 

Lower 

Mississippi 

Upper 

Mississippi 

Pennsyl- 

vanic 

Permic 

.1 

Jurassic 

Comanchic 

Cretacic 

_ 

Eogenic 

'c 

& 

o 

2; 

1 

Qi 

Geologic  time 

Proterozoic 

Cambric 

Ordovicic 

Siluric 

Devonic 

Lower 

Carbonic 

Upper 

CarlMnic 

Permic 

Triassic 

Jurassic 

Lower 

Cretacic 

Upper 

Cretacic 

1  Eocene  j 

1  Oligocene  | 

1 

s 

Pliocene 

Pleistocene 

Recent 

Fig.  86. — Geological  Changes  of  Climate  and  Movements  of  the  Earth’s  Crust.  (After  Schuchert.) 


consisted  of  more  than  one  epoch,  for  red  deposits,  apparently  indicative  of  aridity  or 
warmth,  appear  between  glacial  deposits.  The  number  of  glacial  and  interglacial  epochs 
in  this  period  may  be  considerable,  although  as  yet  our  knowledge  is  incomplete.  In  the 
other  two  glacial  periods  of  the  Proterozoic  era  the  evidence  is  as  yet  so  slight  that  we  can 
not  tell  whether  they  consisted  of  merely  one  epoch  or  of  many. 

Not  even  yet,  however,  as  Professor  Schuchert  goes  on  to  say,  is  the  physical  evidence 
of  former  glacial  climates  exhausted,  for  the  notable  Table  Mountain  tillites  of  South  Africa 
point  to  a  cold  climate  that  occurred  at  least  locally  late  in  Siluric  times.  Finally,  there 
may  have  been  a  seventh  cool  period  in  Liassic,  that  is,  early  Jurassic  time,  but  the  biologic 
knowledge  so  far  at  hand  indicates  that  it  was  the  least  significant  among  the  seven  probably 
cool  to  cold  climates  so  far  discovered  in  the  geological  record.  In  addition  to  the  seven 


CRUSTAL  DEFORMATION  AS  THE  CAUSE  OF  CLIMATIC  CHANGES. 


257 


periods  when  the  climate  was  so  cold  as  to  cause  glaciation  or  a  close  approach  thereto, 
there  have  been  various  other  periods  of  sudden  cooling  similar  in  character  to  glacial 
periods  but  less  marked.  All  of  these  are  indicated  in  the  chart,  figure  91,  which  accom¬ 
panies  Professor  Schuchert’s  paper,  and  part  of  which  is  here  reproduced  in  figure  86. 
The  curves  scarcely  need  explanation.  The  lower  one  indicates  the  probable  course  of 
variations  of  temperature  during  geological  times.  The  high  portions  indicate  a  tropical 
climate  and  the  low  portions  a  frigid  climate.  It  should  be  noted  that  the  curve  is  the 
reverse  of  those  used  in  the  previous  portions  of  this  volume,  in  which  high  places,  not 
low,  indicate  an  approach  toward  the  conditions  which  induce  glaciation.  The  upper 
curve  of  figure  86  indicates  the  degree  of  aridity,  the  high  portions  indicating  great  dryness 
and  the  low  portions  relative  humidity.  It  will  be  seen  at  a  glance  that  in  a  large  number 
of  cases  the  evidences  of  great  aridity  and  of  glaciation  appear  at  about  the  same  time. 
This  may  perhaps  indicate  that  glaciation  and  aridity  are  due  to  the  same  cause.  It  is 
equally  possible,  however,  that  the  approximate  coincidence  of  the  two  phenomena  merely 
indicates  that  we  have  to  deal  with  periods  of  great  climatic  instabilitj'',  during  which  epochs 
of  glaciation  alternate  with  interglacial  epochs  of  aridity.  One  of  the  Proterozoic  glacial 
periods  and  also  the  Permic  and  Pleistocene  periods,  as  we  have  seen,  point  to  this  con¬ 
clusion,  and  the  others  neither  support  nor  oppose  it,  foF our  knowledge  of  them  is  still  so 
fragmentary  that  no  conclusion  is  possible. 

Turning  now  from  the  question  of  the  succession  of  glacial  periods,  let  us  see  what 
Professor  Schuchert  has  to  say  as  to  their  relation  to  movements  of  the  earth’s  crust : 

“Of  the  four  more  or  less  well-determined  glacial  periods  at  least  three,  earliest  Proterozoic, 
Permic,  and  Pleistocene,  occurred  during  or  directly  after  times  of  intensive  mountain-making, 
while  the  fourth,  late  Proterozoic,  apparently  also  followed  a  period  of  elevation.  *  *  *  On  the 
other  hand,  the  very  marked  and  world-wide  mountain-making  period  *  *  *  during  late  Mesozoic  and 
earliest  Eocene  times  was  not  accompanied  by  a  glacial  climate,  but  only  by  a  cooled  one.  The 
cooled  period  of  the  Liassic  also  followed  a  mountain-making  period,  that  of  late  Triassic  times.” 

An  inspection  of  Professor  Schuchert’s  diagram,  as  reproduced  in  figure  86,  shows  that 
the  agreement  of  mountain-making  epochs  and  periods  of  climatic  change  is  even  closer 
than  he  has  indicated.  In  his  diagram  Professor  Schuchert  shows  22  periods  of  mountain¬ 
making.  Among  these  22,  Nos.  1,  4,  5,  10,  and  15  accompany  or  immediately  precede 
great  changes  of  climate.  Nos.  19,  20,  and  possibly  21  are  associated  with  distinct,  but  less 
important  changes,  and  No.  22  is  associated  with  the  great  Pleistocene  glacial  period. 
Small  changes  of  climate  accompany  or  follow  the  mountain-making  epochs  Nos.  2,  6,  8, 
9,  11,  13,  and  17.  The  only  mountain-making  epochs  not  accompanied  by  a  climatic 
change  of  some  sort,  as  indicated  by  Professor  Schuchert’s  lines  of  temperature  and  aridity, 
are  Nos.  3,  7,  12,  and  18 — only  4  out  of  22.  It  is  possible  that  these  mountain-making 
periods  were  also  accompanied  or  followed  by  changes  of  climate,  and  that  this  does  not 
appear  simply  because  the  changes,  like  the  mountain-making,  were  of  relatively  slight 
magnitude  and  hence  have  escaped  detection.  This  would  scarcely  be  surprising,  since  it 
is  only  about  30  years  since  the  possibility  of  Permian  glaciation  began  to  be  seriously 
discussed,  and  practically  all  our  knowledge  of  coolings  of  the  earth’s  climate  aside  from  the 
Pleistocene  and  Permian  glaciations  has  been  obtained  during  the  present  century.  A 
basis  of  18  out  of  22  possible  cases  seems,  then,  to  be  good  ground  for  Professor  Schuchert’s 
statement  that  “cooled  and  cold  climates,  as  a  rule,  occur  during  or  following  periods  of 
marked  mountain-making.”  Yet  the  agreement  between  periods  of  mountain-making 
and  of  cool  climates  is  by  no  means  perfect ;  for,  as  Professor  Schuchert  indicates,  the  degree 
of  cooling  is  not  proportional  to  the  intensity  of  mountain-making.  This  appears  to  be 
especially  noticeable  in  late  Mesozoic  and  early  Eocene  times,  and  to  a  less  extent  in  upper 
Mississippian  and  late  Oligocene.  In  all  these  cases  the  mountain-making  is  proportionally 
much  more  intense  than  the  accompanying  climatic  change.  Moreover,  it  must  be 

18 


258 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


remembered  that  when  we  speak  of  cool  climates  we  do  not  mean  that  the  climate 
became  cooler  merely  among  the  uplifted  mountains.  Of  course  the  fact  that  a  given 
region  was  uplifted  necessarily  made  it  cooler  than  formerly,  but  the  geological  record 
preserves  little  evidence  of  this.  The  subaerial  formations  which  have  come  down  from 
those  early  times  were  almost  wholly  deposited  at  low  altitudes,  for  otherwise  they  could 
not  have  been  preserved.  Many  were  manifestly  laid  down  near  sea-level,  for  they  are 
interstratified  with  marine  deposits.  Moreover,  a  large  part  of  the  evidence  as  to  the 
climate  of  ancient  geological  times  comes  from  marine  fossils.  Accordingly,  when  we 
speak  of  periods  of  cool  and  cold  climates,  we  refer  to  conditions  at  sea-level.  It  may  be 
that  pronounced  crustal  deformation  would  cause  the  earth’s  climate  to  become  cool  even 
at  sea-level,  because  of  changes  in  oceanic  and  atmospheric  circulation.  Possibly  also  the 
reduction  of  the  amount  of  aqueous  vapor  in  the  air  by  reason  of  an  increase  in  the  size 
of  the  continents  would  add  to  this  effect.  Yet,  according  to  the  law  of  chances,  mountain¬ 
making,  and  especially  the  upheaval  of  continents,  ought  often  to  cause  vast  oceanic  areas 
to  become  warmer  than  hitherto  instead  of  colder;  for  cold  currents  would  be  prevented 
from  reaching  low  latitudes  as  often  as  they  would  be  permitted  to  reach  them,  and  warm 
currents  would  be  similarly  affected  whenever  barriers  were  interposed.  Therefore  we 
ought  in  many  cases  to  find  that  periods  of  mountain-making  and  continental  uplift  are 
followed  by  periods  of  warmth  over  a  considerable  portion  of  the  earth.  This  result 
might  be  less  marked  than  a  cooling  effect,  for  any  increase  in  the  number  of  land  barriers 
would  tend  to  isolate  certain  polar  portions  of  the  ocean  and  to  prevent  them  from  being 
warmed  by  currents  from  the  equator.  Nevertheless  we  should  scarcely  expect  to  find  so 
preponderating  a  tendency  toward  cool  conditions,  even  in  low  latitudes,  whenever  pro¬ 
nounced  movements  of  the  earth’s  crust  take  place.  Hence  some  other  cause  of  climatic 
variation  seems  necessary.  Moreover,  such  movements  can  scarcely  account  for  the  com¬ 
paratively  rapid  succession  of  cold  glacial  and  warm,  or  arid,  interglacial  epochs,  a  fact 
which  Professor  Schuchert  takes  care  to  indicate.  Hence,  from  this  point  of  view  also, 
some  other  cause  seems  needed. 

After  discussing  the  relation  of  mountain-making  and  chmate.  Professor  Schuchert 
takes  up  the  new  volcanic  theory  of  climate  and  tests  it  by  the  geological  record.  He  shows 
that  although  mountain-making  and  cool  climates  are  usually  associated,  there  appears 
to  be  no  correspondingly  close  association  between  cool  chmates  and  volcanism.  This  is 
especially  noticeable  at  the  end  of  the  Mesozoic  and  during  the  Eocene,  when  the  greatest 
known  volcanic  activity  of  geological  times  does  not  appear  to  have  produced  any  marked 
glaciation.  Moreover,  the  Permic  and  Pleistocene  glaciations  seem  not  to  have  been 
coincident  with  periods  of  exceptional  volcanic  activity,  but  followed  them  at  intervals 
which,  although  not  of  great  length  geologically,  must  have  been  measured  in  hundreds  of 
thousands  of  years.  This  is  quite  inconsistent  with  the  volcanic  theory,  for  there  is  no 
reason  to  think  that  even  the  finest  volcanic  dust  remains  in  the  atmosphere  more  than 
a  few  years.  Accordingly  unless  further  study  shall  disclose  unexpected  evidence  of 
widespread  volcanic  activity  coincident  with  glaciation,  it  seems  wise  to  accept  Professor 
Schuchert’s  conclusion  that:  “Volcanic  dust  in  the  isothermal  region  of  the  earth  does  not 
appear  to  be  a  primary  factor  in  bringing  on  glacial  chmates.  On  the  other  hand,  it  can 
not  be  denied  that  such  periodically  formed  blankets  against  the  sun’s  radiation  may  have 
assisted  in  coohng  the  climates  during  some  of  the  periods  when  the  continents  were  highly 
emergent.” 

This  conclusion,  based  on  the  whole  extent  of  geological  time,  is  almost  identical  with 
that  which  we  have  previously  reached  from  a  study  of  the  short  period  of  thirty  years 
since  careful  measurements  of  solar  radiation  were  begun,  soon  after  1880. 

One  other  theory  receives  attention  at  the  hands  of  Professor  Schuchert,  and  here  again 
his  conclusion,  based  on  a  vast  lapse  of  time,  agrees  with  that  which  we  have  already 


CRUSTAL  DEFORMATION  AS  THE  CAUSE  OF  CLIMATIC  CHANGES. 


259 


reached  on  the  basis  of  the  changes  during  the  past  two  or  three  thousand  years.  He  can 
not  accept  the  carbonic-acid  theory  of  glaciation,  for  two  reasons :  In  the  first  place,  glacial 
periods  seem  to  come  on  quickly,  whereas  changes  in  the  carbonic-acid  content  of  the  air 
must  be  very  slow.  In  the  second  place,  glacial  epochs  alternate  with  interglacial  epochs 
in  a  way  which  demands  that  the  amount  of  CO2  shall  have  varied  much  more  rapidly 
than  seems  possible.  Finally,  no  glacial  period  seems  to  have  followed  the  enormous 
locking  up  of  carbonic  acid  in  the  vast  limestone  deposits  of  the  Cretacic,  while  strong 
glaciation  followed  the  much  smaller  locking  up  of  CO2  during  the  Miocene  and  Phocene. 
Moreover,  the  conclusions  set  forth  in  earlier  portions  of  this  book  add  still  another  strong 
argument  against  the  carbonic-acid  theory,  for  they  show  that  the  climatic  changes  of 
historic  times  appear  to  be  of  too  long  duration  to  be  explained  on  purely  meteorological 
grounds  and  yet  are  far  too  rapid  to  be  due  to  changes  in  the  amount  of  CO2  in  the  air. 
Having  excluded  the  carbonic-acid  theory  on  these  grounds,  Professor  Schuchert’s  final 
conclusion  is  that  changes  in  the  form  and  size  of  the  continents  and  seas,  together  with 
the  uplifting  of  mountain  ranges  upon  the  land  and  the  diversion  of  oceanic  currents  and 
winds  from  one  area  to  another,  and  the  subsequent  changes  in  the  amount  of  aqueous 
vapor  contained  in  the  air,  have  been  the  chief  factors  in  producing  the  marked  climatic 
variations  which  characterize  the  geological  record.  ‘‘Briefly  then,”  as  he  puts  it,  “we 
may  conclude  that  markedly  varying  climates  of  the  past  seem  to  be  due  primarily  to 
periodic  changes  in  the  topographic  form  of  the  earth’s  surface,  plus  variations  in  the 
amount  of  heat  stored  by  the  oceans.  The  causation  for  the  warmer  interglacial  climates 
is  the  most  difficult  of  all  to  explain,  and  it  is  here  that  factors  other  than  those  mentioned 
may  enter.” 

Let  us  now  sum  up  the  evidence  as  to  the  various  climatic  hypotheses.  Professor 
Schuchert’s  conclusion,  being  based  upon  the  well-verified  agreement  of  two  distinct  types 
of  related  facts,  is  much  more  weighty  than  any  conclusion  based  upon  purely  theoretical 
grounds,  and  there  seems  to  be  good  reason  to  accept  it  as  in  large  measure  correct.  Yet 
it  lacks  finality  in  several  respects.  In  the  first  place,  the  theory  of  crustal  deformation 
makes  no  attempt  to  explain  the  small  climatic  changes  now  in  progress.  Secondly,  it 
can  not  explain  such  occurrences  as  the  marked  changes  which  culminated  about  the  time 
of  Christ,  about  1000  a.  d.,  and  about  1350  a.  d.  Thirdly,  it  can  not  explain  interglacial 
climates.  And  lastly,  it  does  not  explain  why  mountain-making  and  continental  uplift 
are  usually  accompanied  by  cool  climates  even  at  sea-level,  although  the  law  of  chances 
would  indicate  that  part  of  the  time  the  uplifting  of  the  land  should  be  as  potent  in  causing 
parts  of  the  sea  to  become  warmer  as  in  causing  them  to  become  cooler.  The  volcanic 
hypothesis  appears  to  be  a  useful  supplement  to  the  hypothesis  of  crustal  deformation, 
but  it  fails  to  account  for  many  of  the  most  striking  phenomena,  and  would  seem  to  occupy 
a  position  of  only  secondary  importance.  In  the  first  place,  the  occurrence  of  pronounced 
volcanic  activity  during  geologic  times  does  not  appear  regularly  to  coincide  with  pro¬ 
nounced  glaciation.  In  the  second  place,  although  volcanoes  can  be  shown  to  have  had 
a  distinct  effect  upon  terrestrial  temperature  in  the  period  since  measurements  of  the  sun 
began  to  be  made  with  accuracy,  the  effect  is  sporadic.  It  appears  to  be  by  no  means  so 
important  as  the  effect  which  seems  to  be  exerted  by  changes  in  the  sun,  if  we  may  judge 
from  the  agreement  of  the  sun-spot  curve  with  the  curve  of  the  earth’s  temperature.  Our 
third  hypothesis,  that  of  carbonic-acid  gas,  seems  to  be  unsatisfactory  because  it  can  not 
account  for  the  rapidity  with  which  climatic  changes  take  place,  and  because  times  of 
maximum  glaciation  do  not  regularly  follow  times  when  the  maximum  amount  of  CO2  is 
withdrawn  from  the  atmosphere.  This  does  not  mean  that  we  reject  the  idea  that  carbonic 
acid  is  an  important  cause  of  climatic  changes,  but  merely  that  it  seems  safer  to  assign  to 
it  a  contributory  r61e.  Variations  in  the  amount  of  carbonic-acid  gas  in  the  atmosphere 
from  year  to  year,  apart  from  human  manipulation,  probably  occur,  though  this  has  never 
been  demonstrated  by  actual  observation. 


260 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Turning  now  to  the  solar  hypothesis,  we  find  that  the  only  serious  objection  to  it  is 
that  we  do  not  possess  any  direct  evidence  that  the  intensity  of  solar  radiations  has  varied 
greatly  in  past  times.  In  the  nature  of  the  case,  no  such  evidence  can  ever  be  forthcoming. 
We  do  know,  however,  that  during  the  few  decades  since  measurements  have  been 
possible,  it  has  been  proved  beyond  question  that  the  intensity  of  solar  radiation  actually 
varies,  although  the  amount  of  variation  may  be  small.  Moreover,  historic  records  of  sun¬ 
spots  tell  us  that  the  sun’s  activity  has  varied  in  the  past,  and  there  are  indications  that 
at  certain  periods  the  number  or  size  of  the  sun-spots  was  greater  than  recently.  When  we 
compare  solar  changes  with  variations  in  the  earth’s  climate  during  the  past  few  decades, 
we  find  that  the  two  agree  in  many  different  ways.  We  also  find  that  if  allowance  is  made 
for  the  unequal  distribution  of  the  sun’s  insolation  over  the  earth’s  surface  and  for  the 
effect  of  volcanic  dust  in  shutting  out  the  sun’s  heat,  many  of  the  apparent  disagreements 
between  solar  and  terrestrial  phenomena  disappear.  If  we  suppose  that  in  the  past  the 
sun’s  variations  were  like  those  of  the  present,  but  on  a  larger  scale,  we  find  an  explanation 
of  climatic  change  which  appears  to  satisfy  all  the  requirements.  We  may  suppose  that 
at  certain  times  the  sun  was  stimulated  to  unusual  activity,  just  as  it  is  to-day  when  we 
have  periods  of  unusually  numerous  sun-spots,  but  to  a  greater  degree.  This  stimulation 
would  cause  an  increase  in  all  the  phenomena  associated  with  sun-spots.  If  the  latest  con¬ 
clusions  of  Hale  and  others  are  correct,  the  sun-spots  are  violent  perturbations  of  a  cyclonic 
character,  whereby  material  from  the  lower  part  of  the  sun’s  atmosphere  is  carried  into 
the  upper  part.  This  process,  according  to  an  interesting  suggestion  made  by  Humphreys 
and  quoted  in  Professor  Schuchert’s  portion  of  this  volume,  might  so  increase  the  density 
of  the  solar  atmosphere  that  an  appreciable  share  of  the  sun’s  radiant  energy  would  be 
prevented  from  escaping  into  space.  This  would  produce  the  same  effect  as  the  presence 
of  dust  in  the  earth’s  atmosphere,  and  would  cause  the  earth’s  climate  to  become  cool. 
The  degree  of  cooling  upon  the  earth,  and  upon  the  other  planets,  where  the  same  result 
would  ensue,  would  depend  upon  the  amount  of  material  in  the  solar  atmosphere.  The 
sun  itself  might  conceivably  be  hotter  than  before,  and  probably  would  be,  although  the 
effect  upon  outside  bodies  would  be  diminished.  The  material  thrown  into  the  solar 
atmosphere  would  presumably  be  in  the  most  comminuted  form,  perhaps  molecular,  and 
part  might  even  escape  into  space.  The  remainder,  however,  would  gradually  fall  back 
toward  its  place  of  origin.  Thus  the  solar  atmosphere  would  become  clearer,  although 
the  process  would  take  a  long  time.  As  the  atmosphere  grew  clearer,  more  and  more  of 
the  sun’s  radiation  would  escape  into  space  and  the  earth  would  become  correspondingly 
warmer.  If  the  sun  were  actually  hotter  than  normal,  the  clearing  of  its  atmosphere  would 
give  rise  to  an  interglacial  epoch  characterized  by  unusual  warmth  or  by  aridity.  This 
would  last  until  renewed  solar  activity  caused  the  ejection  of  more  material  and  the  solar 
atmosphere  once  more  became  dense,  thus  causing  another  glacial  epoch.  The  processes 
here  suggested,  together  with  those  discussed  in  the  following  paragraph,  would  cause  cold 
climates  to  develop  rapidly  and  pass  away  more  slowly.  This  would  correspond  with  the 
conclusions  of  geology,  and  would  also  agree  with  the  changes  of  the  last  3,000  years  in 
California,  where  the  curve  of  the  sequoia  usually  rises  more  rapidly  than  it  falls. 

At  this  point  we  must  consider  what  would  be  happening  to  the  earth’s  crust  at  such  a 
time  of  unusual  activity  in  the  sun.  According  to  Professor  Schuchert  the  time  when 
the  sun  would  be  filling  its  atmosphere  with  ejected  material,  and  thus  preparing  the 
way  for  a  cool  period  upon  the  earth,  would  be  likely  to  be  a  period  of  pronounced  crustal 
deformation.  In  other  words,  a  stimulation  of  the  earth’s  interior  appears  to  take  place  at 
the  same  time  that  our  hypothetical  stimulation  of  the  sun  takes  place.  The  stimulation 
of  the  earth  causes  crustal  deformation,  the  upheaval  of  continents  and  mountains,  the 
formation  of  barriers  between  adjoining  portions  of  the  sea,  and  a  general  change  in  the 
oceanic  and  atmospheric  circulation  with  a  consequent  readjustment  of  climate.  It  gen- 


CRUSTAL  DEFORMATION  AS  THE  CAUSE  OF  CLIMATIC  CHANGES. 


261 


erally  also  causes  volcanic  activity  which  may  be  of  the  quiet  type  where  vast  deposits  of 
liquid  lava  are  formed,  as  happened  in  the  Deccan,  or  of  the  violent,  explosive  type.  If 
explosive  eruptions  occur,  still  further  chmatic  changes  may  be  induced.  To  this  would 
be  added  the  effect  of  the  great  elevation  and  extent  of  the  land  in  causing  rapid  weathering 
and  erosion.  Under  such  circumstances  much  CO2  is  set  free  from  the  rocks,  and  may 
in  time  become  so  abundant  as  to  appreciably  raise  the  earth’s  temperature.  Thus  it 
appears  that  in  our  completed  hypothesis  solar  changes  stand  first  in  importance.  With 
them,  however,  and  perhaps  inseparable  from  them,  occur  changes  in  the  earth’s  interior 
whereby  crustal  deformation  is  induced.  This,  in  turn,  is  usually  associated  closely  with 
volcanic  eruptions,  and  rarely  takes  place  without  them.  It  also  gives  rise  to  the  processes 
whereby  the  amount  of  CO2  is  increased.  All  four  types  of  activity,  solar,  crustal,  volcanic, 
and  erosional,  appear  to  have  a  direct  effect  upon  terrestrial  climate.  An  accurate  weighing 
of  their  relative  importance  may  perhaps  do  much  to  explain  the  earth’s  climatic  history. 

The  conclusion  just  stated  seems  to  carry  with  it  the  assumption  that  there  is  some 
relation  between  deformation  of  the  earth’s  crust  and  periods  of  instability  and  variable 
radiation  in  the  sun.  Such  an  assumption  leads  at  once  to  the  inquiry  whether  any  possible 
cause  can  be  assigned  for  coincident  or  related  activities  of  the  two  bodies.  It  is  easy 
to  speculate  as  to  hypothetical  changes  in  the  relation  of  the  solar  system  to  the  rest 
of  the  universe,  as  to  possible  magnetic  variations,  or  as  to  the  passage  of  the  solar  system 
through  portions  of  space  characterized  by  conditions  different  from  those  in  which  it 
now  finds  itself,  but  such  speculation  is  fruitless.  Another  line  of  inquiry  relates  to  the 
possible  passage  of  our  system  through  swarms  of  meteorites  so  large  and  numerous 
that  their  collisions  with  the  various  members  of  the  solar  system  would  produce  appre¬ 
ciable  effects,  but  here  again  we  have  not  the  slightest  basis  for  theorizing.  It  is  perhaps 
more  probable  that  the  gravitative  or  magnetic  forces  of  the  sun  itself  cause  that  body  alter¬ 
nately  to  fall  into  periods  of  quiescence  or  activity.  This  activity  may  be  conununicated 
to  the  earth  in  some  such  way  as  that  in  which  the  magnetic  changes  of  the  sun  are  known 
to  produce  an  immediate  terrestrial  effect.  Other  lines  of  thought  might  also  be  suggested, 
but  even  to  mention  them  would  scarcely  be  worth  while.  All  that  we  can  say  is  that,  in 
spite  of  the  absence  of  any  assignable  cause,  there  seems  to  be  some  ground  for  the  hypothe¬ 
sis  that  throughout  the  course  of  geological  history  disturbances  of  the  earth  and  of  the 
sun  have  occurred  at  about  the  same  time.  According  to  our  present  hypothesis,  dis¬ 
turbances  of  the  earth  seem  to  have  caused  deformation  of  the  crust,  accompanied  often¬ 
times  by  volcanic  outbursts,  and  causing  a  redistribution  of  climatic  zones  in  accordance 
with  the  new  outlines  of  continents  and  the  new  courses  of  winds  and  currents.  Those  of 
the  sun,  on  the  other  hand,  seem  to  have  caused  that  body  to  throb  with  pulsations  of 
various  lengths  whose  greatest  effects  are  seen  in  glacial  and  interglacial  epochs,  while  the 
minor  effects  appear  in  little  cycles  like  those  whose  average  lengths  now  appear  to.  be 
about  11  and  35  years.  Because  of  the  earth’s  small  size  or  rigidity,  its  activity  appears 
to  have  come  to  an  end  more  quickly  than  that  of  the  sun,  as  appears  from  the  fact  that 
in  general  the  upheaval  of  continents  and  mountain  systems  has  preceded  the  periods  of 
most  marked  climatic  instability. 

Beyond  this  it  would  at  present  be  useless  to  attempt  to  go.  Our  suggestion  of  a  possible 
relation  between  the  internal  activities  of  the  earth  and  the  sun  is  merely  one  among  several 
working  hypotheses.  It  seems  to  be  the  logical  conclusion  of  our  study  of  terraces, 
lacustrine  strands,  ruins,  the  growth  of  trees,  the  rise  and  fall  of  civilizations,  and  the 
occurrence  of  glacial  periods  in  geological  times.  Yet  its  truth  or  falsity  has  nothing  to 
do  with  the  verity  of  our  hypotheses  as  to  these  other  matters.  It  may  prove  wholly 
wrong,  but  that  does  not  in  the  least  affect  them.  In  the  same  way  some  other  hypotheses, 
such  as  our  inferences  as  to  the  relation  of  pre-Columbian  civilization  to  changes  of  climate, 
may  also  prove  to  be  insufficiently  grounded  and  may  have  to  be  much  modified,  but  this 


262 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


does  not  affect  the  remaining  conclusions  of  this  volume.  To  a  less  degree  the  same  is 
true  of  our  hypotheses  as  to  the  exact  mechanism  by  which  the  conditions  of  one  climatic 
zone  may  be  shifted  into  another. 

All  these  hypotheses  with  their  varying  degrees  of  certainty  are  subsidiary  to  one 
main  conclusion.  They  fall  if  it  proves  untrue,  but  if  they  prove  untrue  its  position  remains 
unchanged,  for  it  does  not  depend  upon  them.  That  upon  which  it  does  depend  is  the 
convergence  of  a  large  number  of  lines  of  evidence  upon  the  single  point  of  whether  the 
climate  of  the  earth  has  changed  appreciably  during  the  past  few  thousand  years  since 
history  began.  All  the  evidence  seems  to  unite  in  indicating  that  such  a  change  has  taken 
place,  and  that  it  has  been  of  a  pulsatory  nature.  This,  then,  is  our  main  conclusion,  the 
one  point  around  which  all  else  centers.  Doubtless  the  details  as  to  the  time  of  changes, 
and  especially  as  to  their  relation  to  one  another  in  different  parts  of  the  world,  will  require 
modification,  for  we  have  been  able  to  gather  only  a  small  part  of  the  facts.  This  matters 
little,  however,  provided  we  are  headed  in  the  right  direction.  The  only  essential  is  that 
each  new  venture  shall  advance  us  one  short  step  on  that  most  wonderful  of  roads  which 
leads  to  the  knowledge  of  what  some  men  call  the  law  of  the  universe,  and  others,  more 
deeply  thinking,  call  the  law  of  God. 


PART  II. 


CLIMATES  OF  GEOLOGIC  TIME. 


By  CHARLES  SCHUCHERT 

Professor  of  Paleontology  in  Yale  University 


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CHAPTER  XXI. 


CLIMATES  OF  GEOLOGIC  TIME 


By  Charles  Schuchert. 


The  ancient  philosophers  imagined  that  the  earth  arose  out  of  darkness  and  chaos  and 
that  its  present  form  and  condition  came  about  gradually  through  the  creative  acts  of  an 
omniscient  and  omnipotent  God.  Certain  Greek  philosophers  tell  us  that  the  world  had 
its  origin  in  a  primeval  chaos;  others  that  it  arose  out  of  water  or  an  all-pervading  primeval 
substance  with  inherent  power  of  movement;  that  the  energy  of  this  primal  matter  deter¬ 
mined  heat  and  cold,  and  that  the  stars  originated  from  fire  and  air.  It  was  Empedocles 
(492-432  B.  c.)  who  first  told  us  that  the  interior  of  the  earth  was  hot  and  composed  of 
molten  material,  an  opinion  he  formulated  after  seeing  the  volcanic  activity  of  the  Sicilian 
Mount  Etna,  in  whose  crater  he  is  said  to  have  met  his  fate. 

The  geology  of  to-day  still  teaches  that  the  interior  of  the  earth  is  very  hot,  but  that 
the  material  of  which  it  consists  is  as  dense  and  rigid  as  steel,  and  that  Httle  of  the  interior 
high  temperatures  attains  the  earth’s  surface  because  of  the  low  conductivity  of  the  rocky 
and  far  less  dense  outer  shell.  The  older  geologists  believed  that  this  shell  originally  was 
thin,  and  that  therefore  much  heat  was  radiated  into  space,  this  idea  being  a  natural  result 
of  the  Laplacian  theory  of  earth  origin.  In  other  words,  they  held  that  the  earth  was  once 
a  very  small  star  which,  in  the  course  of  the  eons,  gradually  cooled  and  formed  a  crust. 
Therefore  it  was  postulated  that,  because  the  crust  formerly  must  have  been  thin,  life 
began  in  hot  waters  and  the  climates  of  the  geologic  past  were  hot,  with  dense  atmospheres 
charged  with  far  more  carbonic  acid  and  water  vapor  than  they  now  hold.  The  present 
type  of  climate  with  zonal  belts  of  decidedly  varying  temperature  and  polar  ice-caps  was 
thought  to  be  of  very  recent  origin,  resultant  from  a  much  thickened  rocky  crust.  All 
of  these  conceptions  are  now  greatly  modified  by  the  planetesimal  hypothesis  of  Professors 
Chamberlin  and  Moulton,  which  teaches  of  an  earth  accreting  around  a  primordial  cold 
nucleus  through  the  infalling  of  small  cold  bodies,  the  planetesimals,  all  of  this  material 
being  derived  from  a  spiral  nebular  mass  formed  by  the  colliding  of  two  large  bodies.  As 
the  nuclear  earth  grew  in  dimensions,  so  also  was  increased  the  gravitative  pressure, 
gradually  developing  central  heat  which  spread  to  the  surface  and  there  broke  out  in  a 
long  period  of  volcanic  activity. 

Our  knowledge  of  glacial  climates  had  its  origin  in  the  Alps,  the  land  of  magnificent 
scenery  and  marvelous  glaciers,  through  the  work  of  Andreas  Scheuzer,  early  in  the 
eighteenth  century.  This  was  at  first  only  a  study  of  the  interesting  local  glaciers,  but  out 
of  it  gradually  came  about,  especially  through  the  studies  of  De  Saussure,  Hugi,  Venetz, 
Charpentier,  Schimper,  and  Louis  Agassiz,  the  application  of  conditions  observed  in  the 
Alps  to  the  very  widely  distributed  foreign  boulders  known  as  erratics  and  the  hetero¬ 
geneous  accumulations  of  sands,  clays,  and  boulders  called  tills.  The  engineer  Venetz  in 
1821  pointed  out  that  the  Alpine  glaciers  had  once  been  of  far  greater  size,  and  that  glaci¬ 
ation  had  been  on  a  scale  of  enormous  magnitude  in  some  former  period.  By  degrees  the 
older  conception  that  the  erratics  and  tills  were  of  flood,  river,  or  iceberg  origin  gave  way 
to  the  theory  of  colder  climates  and  glaciers  of  continental  extent.  It  was  shown  that 
the  reduced  temperature  was  finally  succeeded  by  greater  warmth,  and  that  in  the  wake 

265 


266 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


of  the  melting  glaciers  the  land  was  strewn  with  erratics,  with  thick  accumulations  of 
heterogeneous  rocks  deposited  at  the  edge  of  ice-sheets  and  known  as  moraines,  and  with 
great  fans  of  boulder-clays  and  sands,  all  of  this  being  the  diluvium  or  deluge  material  of 
the  older  philosophers  and  the  drift  or  tills  of  modern  students  of  earth  science. 

Throughout  more  than  a  century  of  study  we  have  learned  how  glaciers  do  their  work 
and  what  results  are  accomplished  by  their  motion  plus  the  action  of  temperature,  air,  and 
water.  The  present  geographic  distribution  of  the  glaciers,  together  with  that  of  the 
glacial  deposits,  shows  us  that  during  the  Pleistocene  or  glacial  period  the  temperatme  of 
the  entire  earth  was  lowered.  We  also  know  that  this  cold  period  was  not  a  uniformly 
continuous  one,  but  that  during  the  Pleistocene  there  were  no  less  than  four  intermediate 
warmer  climates,  so  warm  indeed  that  during  one  of  them  Hons  and  hippopotamuses  lived 
in  western  Europe  along  with  primitive  man.  We  may  now  be  living  in  another  inter¬ 
glacial  warm  period,  though  more  probably  we  are  just  emerging  from  the  Pleistocene  ice 
age.  Figure  87  gives  the  known  distribution  of  Pleistocene  glacial  materials. 


Fig.  87. — Map  of  Pleistocene  Glaciation. 


With  the  reduction  of  temperature,  great  variations  also  took  place  in  the  local  supply 
of  moisture,  in  the  number  of  dark  days,  and  in  the  air  currents.  How  great  these  changes 
were  in  Pleistocene  time  is  now  being  revealed  to  us  through  the  work  of  the  geologists, 
paleontologists,  and  ethnologists  of  Europe,  where  this  record  is  far  more  detailed  than  in 
North  America.  These  observations  picture  a  fierce  struggle  on  the  part  of  the  hardier 
organisms  against  the  colder  climates,  a  blotting  out  of  those  addicted  to  confirmed  habits 
and  to  warmer  conditions,  and  a  driving  southward  of  certain  elements  of  the  flora  and 
fauna  from  the  glaciated  into  the  non-glaciated  regions.  The  result  was  the  disestablish- 


CLIMATES  OF  GEOLOGIC  TIME, 


267 


ment  of  the  entire  organic  world  of  the  Pleistocene  lands,  other  than  that  of  the  tropics. 
More  than  once  man  and  his  organic  surroundings  have  been  forced  to  wander  into  new 
regions;  the  hfe  of  cool  to  cold  climates  has  dispossessed  that  of  milder  temperatures,  and 
with  each  moderation  of  the  climate  the  hardier  floras  and  faunas  have  advanced  with  the 
retreating  glaciers,  or  become  stranded  and  isolated  in  the  mountains.  As  the  organic 
world  is  dependent  upon  sunlight,  temperature,  and  moisture,  it  is  not  difficult  to  see  why 
these  same  factors  are  essential  to  man  and  his  civilization. 

PERMIC  GLACIATION. 

Hardly  had  the  Pleistocene  glacial  climate  been  proven  when  geologists  began  to  point 
out  the  possibility  of  earlier  ones.  An  enthusiastic  Scotch  writer.  Sir  Andrew  Ramsay, 
in  1855  described  certain  late  Paleozoic  conglomerates  of  middle  England,  which  he  said 
were  of  glacial  origin,  but  his  evidence,  though  never  completely  gainsaid,  has  not  been 
generally  accepted.  In  the  following  year,  an  Englishman,  Dr.  W,  T.  Blanford,  said  that 


Fig.  88. — Paleogeography  and  Glaciation  of  Early  Permic  Times. 


the  Talchir  conglomerates  occurring  in  central  and  southern  India  were  of  glacial  origin, 
and  since  then  the  evidence  for  a  Permic  glacial  period  has  been  steadily  accumulating. 
The  land  of  ancient  tills  (tillites  of  geologists)  is  Africa,  and  here  in  1870  Sutherland  pointed 
out  that  the  conglomerates  of  the  Karoo  formation  were  of  glacial  origin,  and,  fmther, 
that  they  rest  on  a  land  surface  which  has  been  grooved,  scratched,  and  polished  by  the 
movement  of  glaciers.  Australia  also  has  Permic  glacial  deposits.  It  is  only  very  recently 
that  the  evidence  found  in  many  places  in  the  southern  hemisphere  has  become  widely 
known,  but  so  convincing  is  this  testimony  that  all  geologists  are  now  ready  to  accept  the 
conclusion  that  a  glacial  climate  was  as  widespread  in  Permic  time  as  was  that  of  tfie 


268 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Pleistocene.  This  time  of  organic  stress,  curiously,  did  not  affect  the  polar  lands,  but 
rather  those  regions  bordering  the  equatorial  zone,  while  the  temperate  and  arctic  zones 
of  the  northern  hemisphere  were  not  glaciated,  but  seem  to  have  had  winters  alternating 
with  summers.  The  lands  that  were  more  or  less  covered  with  snow  and  ice  lay  on  each 
side  of  the  equator — that  is,  roughly,  from  20°  to  40°  north  and  south  of  this  hne,  as  may 
be  seen  in  figure  88. 

Geologists  now  accept  the  geographical  occurrence  of  tillite  deposits  formed  in  early 
Permic  time  as  follows:  Throughout  South  Africa  (widely  distributed  and  with  much 
fossil  evidence,  thickness  of  tillites  up  to  1,130  feet) ;  Tasmania;  western,  southern,  eastern, 
and  central  Australia  (tillites  up  to  1,300  feet  thick,  both  land  and  marine  fossils); 
peninsular  and  northwestern  India;  southeastern  Brazil  (of  wide  distribution,  with  land 
floras  and  some  marine  invertebrates);  northern  Argentina;  and  the  Falkland  Islands. 
“It  may  be  added  that  the  plant  beds  of  the  Gondwana  associated  with  the  glacial  deposits 
found  near  Herat  [Afghanistan]  are  much  like  beds  found  in  Russian  Turkestan  and 
Elburz,  in  Armenia,  suggesting  a  still  farther  extension  to  the  west  [of  India],  and  that  a 
probably  glacial  conglomerate  is  known  from  the  Urals”  (Coleman,  1908a:  350).  Heritsch 
records  the  presence  of  tillites  in  the  Alps  and  Freeh  points  out  that  a  scratched  surface 
occurs  in  the  Ruhr  coal  field  of  Germany,  on  which  the  Rothliegende  rests  (Freeh,  1908:  74). 
The  Roxbury  conglomerate  with  a  thickness  of  500  to  600  feet  occurs  in  the  vicinity  of 
Boston  and  is  interpreted  as  a  tillite  (Sayles  and  La  Forge:  723-4).  Then,  too,  the  Lower 
Permic  (Buntsandstein)  of  western  Europe  is  now  thought  to  indicate  not  only  an  arid  but 
probably  also  a  cool  climate. 

The  greater  part  of  these  glacial  deposits  is  ground  moraines  or  morainic  material 
carried  by  the  land  ice  into  the  sea.  Their  wide  distribution  in  the  southern  hemisphere 
clearly  indicates  that  glaciation  there  was  as  effective  in  earhest  Permic  time  as  was  that 
of  the  Pleistocene  of  the  northern  hemisphere.  This  Permic  glaciation  caused  the  devel¬ 
opment  in  the  southern  hemisphere  of  a  pecuhar  hardy  flora — the  Glossopteris  flora — of 
which  very  little  is  known  in  the  northern  hemisphere.  Of  this  cold-climate  flora  the 
invaders  and  advance  migrants  arrived  in  Asia  and  Europe  not  before  Middle  Permic  time. 

In  Africa  and  India  the  glacial  condition  appears  to  have  been  continuous  during  early 
Permic  time,  and  there  is  as  yet  no  convincing  evidence  here  for  interglacial  warmer 
climates  such  as  occurred  in  the  Pleistocene.  In  Brazil,  however,  the  evidence  appears  to 
indicate  one  warmer  between  two  colder  periods,  and  in  New  South  Wales  there  is  evidence 
of  a  series  of  recurrent  colder  and  warmer  climates.  This  condition  is  stated  by  Chamber¬ 
lin  and  Salisbury  as  follows: 

“In  South  Australia,  above  a  series  of  Coal  Measures,  the  plants  of  which  are  of  the  normal 
Carboniferous  types,  there  is  a  series  of  marine  beds  alternating  with  beds  which  contain  land 
plants  unlike  those  of  the  Coal  Measures  below.  Considerable  beds  of  coal  are  also  included  in 
the  series.  Interstratified  with  these  marine  strata  and  coal  seams  there  are  considerable  beds 
of  conglomerate  of  distinctive  glacial  type.  Some  of  the  bowlders  of  the  conglomerate  are  striated 
in  such  a  way  as  to  leave  no  doubt  as  to  their  glacier  origin.  Furthermore,  the  substratum  on 
which  the  bowlder  beds  rest  has  been  repeatedly  observed  to  be  grooved  and  polished,  like  roches 
moutonnees.  *  *  * 

“The  number  of  well-defined  bowlder  beds  is  in  places  (Bacchus  Marsh  District,  Victoria) 
not  less  than  nine  or  ten,  and  some  of  them  have  a  thickness  of  fully  200  feet.  The  marine  beds 
with  which  they  are  intercalated  have  an  aggregate  thickness  of  2,000  feet  or  more,  and  30  to 
40  feet  of  coal  are  included  between  the  highest  and  lowest  of  the  bowlder  beds.  The  recurrence 
of  the  bowlder  beds  points  to  the  repeated  recurrence  of  glacial  conditions,  and  the  great  thickness 
both  of  clastic  beds  and  of  the  included  coal  point  to  the  great  duration  of  the  period  through  which 
the  several  glacial  epochs  were  distril^uted ”  (632). 

In  Africa,  in  the  southern  Dwyka  region,  there  is  also  some  evidence  for  interglacial 
warmer  periods  (Coleman,  1908a:  360). 


CLIMATES  OP  GEOLOGIC  TIME. 


269 


DEVONIC  GLACIATION. 

In  South  Africa  there  occurs,  beneath  Lower  Devonic  marine  strata,  the  5,000-feet- 
thick  Table  Mountain  series,  essentially  of  quartzites  with  zones  of  shales  or  slates,  which 
has  striated  pebbles  up  to  15  inches  long,  found  in  pockets  and  seemingly  of  glacial  origin. 
There  are  here  no  t3q)ical  tillites  and  no  striated  undergrounds  have  so  far  been  discov¬ 
ered.  While  the  evidence  of  the  deposits  appears  to  favor  the  conclusion  that  the  Table 
Mountain  strata  were  laid  down  in  cold  waters  with  floating  ice  derived  from  glaciers,  it 
is  as  yet  impossible  to  assign  to  these  sediments  a  definite  geologic  age.  They  are  certainly 
not  younger  than  the  Lower  Devonic,  but  it  has  not  yet  been  established  to  what  period 
of  the  early  Paleozoic  they  belong. 

Elsewhere  than  in  South  Africa,  late  Siluric  or  early  Devonic  tilhtes  are  unknown. 
It  is  desirable  here,  however,  to  direct  attention  to  the  supposed  tillites  mentioned  by 
Ramsay  and  found  in  the  north  of  England  in  the  Upper  Old  Red  Sandstone  of  late  Devonic 
time.  Geikie  (1903:  1001,  1011)  states  that  this  “subangular  conglomerate  or  breccia 
recalls  some  glacial  deposits  of  modern  time.”  Jukes-Brown  in  his  book,  “  The  Building  of 
the  British  Isles,”  1911,  writes  of  arid  Devonic  climates,  but  does  not  mention  tillites  nor 
glacial  climates.  Further  details  as  to  this  and  other  pre-Permic  glaciations  are  given 
in  the  Supplementary  Notes  at  the  end  of  this  chapter  (pp.  290-296),  chiefly  in  the  form 
of  quotations  from  original  sources. 

CAMBRIC  GLACIATION. 

Unmistakable  tillites,  thought  to  be  of  earliest  Cambric  age,  have  been  described  by 
Howchin  and  David  from  southern  Australia  and  by  Willis  and  Blackwelder  from  China. 
In  both  cases  the  evidence  as  to  age  is  open  to  question,  as  the  tillites  are  either  sharply 
separated  from  the  overhung  Cambric  deposits  or  these  strata  have  no  fossils  to  fix  their 
age,  thus  leading  to  the  inference  that  the  tillites  are  more  probably  of  late  Proterozoic 
time.  In  Arctic  Norway  occur  other  tilhtes  at  the  base  of  the  thick  Gaisa  formation. 
These  deposits  also  were  formerly  regarded  as  of  Paleozoic  age,  but  Norwegian  geologists 
now  refer  them  to  the  Proterozoic.  All  of  these  tillites  are  best  referred  to  the  vast  era 
previous  to  the  Cambric  period. 

LATEST  PROTEROZOIC  GLACIATION. 

Australia. — In  southern  Australia,  conformably  beneath  marine  and  fossiliferous  Lower 
Cambric  strata  but  sharply  separated  from  them,  occur  tillites  of  wide  distribution.  They 
extend  from  20  miles  south  of  Adelaide  to  440  miles  north  of  the  same  city,  with  an  east- 
and-west  spread  of  200  miles.  Boulder-clay  has  also  been  discovered  on  the  west  coast  of 
Tasmania.  The  tillites  range  in  thickness  from  about  600  to  1,500  feet  and  occur  at  the  top 
of  a  vast  pile  of  conglomerates,  grits,  feldspathic  quartzites,  slates,  and  phyllites,  whose 
exact  age  is  unknown  because  as  yet  no  fossils  have  been  discovered  in  them.  (See  figure  89.) 

According  to  Howchin,  the  tillite  consists  “mainly  of  a  ground-mass  of  unstratified, 
indurated  mudstone,  more  or  less  gritty,  and  carrying  angular,  subangular,  and  rounded 
boulders  (up  to  11  feet  in  diameter),  which  are  distributed  confusedly  through  the  mass. 
It  is,  in  every  respect,  a  characteristic  till  ”  (1908 :  239) .  The  first  scratched  boulders  were 
observed  in  1901  and  now  they  are  known  by  the  “thousands”  (David).  They  range  in 
size  up  to  about  10  feet  long.  So  far,  no  striated  underground  or  glaciated  floor  has  been 
discovered,  and  both  Howchin  and  David  hold  that  the  tillite  was  formed  at  or  near  sea- 
level  in  fresh  or  brackish  water  with  floating  icebergs.  The  rocks  of  the  tills,  David  thinks, 
came  from  the  south.  The  tilhte  is  now  found  from  below  sea-level  to  about  1,000  feet 
above  the  sea.  These  tilhtes  and  all  of  the  enormous  mass  of  coarse  deposits  below  thern, 
which  is  at  least  several  miles  thick,  the  Australian  geologists  regard  as  of  Lower  Cambric 
age,  because  overlying  them  occur  fossils  of  this  time.  The  contact  between  the  tillite 


270 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


and  the  marine  Cambric  is  always  a  sharp  one,  leading  to  the  inference  that  the  sea  of  this 
time  transgressed  over  an  old  flat  land.  Under  these  circumstances,  deposition  was  not 
continuous,  for  the  geologic  section  is  here  broken  between  the  tillite  and  the  Cambric 
deposits,  indicating  that  the  age  of  the  former  is  rather  late  Proterozoic  than  early  Paleozoic. 
From  the  evidence  of  the  Lower  Cambric  life,  to  be  presented  later,  we  shall  see  that’  the 
waters  of  this  time,  the  world  over,  were  of  tropical  or  subtropical  temperature,  conditions 
not  at  all  in  harmony  with  the  supposed  glacial  climates  of  earliest  Cambric  time.  (For 
further  detail  see  pp.  291-93.) 


The  Norwegian  occurrence  shown  by  an  empty  circle  on  this  map  is  supposed  to  be  late  Proterozoic,  but  there  is  doubt  as  to  the  exact 
date.  The  occurrence  in  Great  Britain  and  also  the  occurrences  indicated  by  diagonal  lines  are  undated  Proterozoic. 

Arctic  Norway. — As  long  ago  as  1891,  Doctor  Reusch  described  unmistakable  tillites 
in  the  Gaisa  formation  in  latitude  70°  N.  along  the  Varanger  Fiord  of  Arctic  Norway. 
Similar  deposits  are  also  known  farther  east  on  Kildin  Island,  and  on  Kanin  Peninsula 
at  Pae  (Ramsay,  1910).  At  flrst  the  age  of  these  deposits  was  thought  to  be  late  Paleozoic 
and  even  Triassic,  but  the  Swedish  geologists  now  correlate  the  Gaisa  with  the  Sparagmite 
formation,  one  of  the  members  of  the  Seve  series.  As  the  latter  is  overlain  by  the  Lower 
Cambric  fauna  it  appears  best  to  refer  the  Gaisa  formation  to  the  top  of  the  Proterozoic 
series.  The  tillite  occurs  at  the  very  base  of  the  Gaisa  formation  and  overlies  the  ancient 
and  eroded  granites.  Strahan  reinvestigated  the  area  originally  studied  by  Reusch  and 
his  description  of  the  geologic  phenomena  must  convince  anyone,  not  only  that  here  are 
intercalated  thin  zones  of  sandstone  and  tillite  in  a  series  of  red  shales  (these  may  indicate 
warmer  and  arid  interglacial  chmates),  but  as  well  that  the  tillite  rests  upon  a  striated 
sandstone,  the  very  ground  over  which  the  glacier  moved.  Strahan  further  states  that 


CLIMATES  OF  GEOLOGIC  TIME. 


271 


“the  Gaisa  Beds,  so  far  as  I  saw  them,  do  not  suggest  the  immediate  neighbourhood  of 
a  mountain-region,  for  such  conglomerates  as  they  contain  are  neither  coarse  nor  plenti¬ 
ful”  (1897 :  145).  Again  we  have  the  evidence  of  tillites  formed  on  low  grounds  and  not  in 
the  mountains.  (For  further  detail  see  pp.  292-3.) 


UNDATED  PROTEROZOIC  GLACIATION. 

The  following  occurrences  of  tillites  do  not  appear  to  be  of  latest  Proterozoic  time, 
as  do  those  of  Australia  and  Norway.  They  are  therefore  held  apart  under  a  separate 
heading  from  the  tilKtes  of  earliest  and  latest  Proterozoic  time. 

North  America. — Professor  Coleman  states  that  “Doctor  Bell  reports  boulders  reaching 
diameters  of  3  feet  8  inches,  having  grooves  like  glacial  striae,  in  a  conglomerate  with 
sandy  matrix  belonging  to  the  Keweenawan  of  Pointe  aux  Mines,  near  the  southeast  end 
of  Lake  Superior.  Messrs.  Lane  and  Seaman*  describe  a  Lower  Keweenawan  conglomerate 
as  containing  ‘  a  wide  variety  of  pebbles  and  large  boulders,  in  structure  at  times  suggestive 
of  till,’  from  the  south  shore  of  Lake  Superior”  (1908a:  354). 

India. — In  peninsular  India  occurs  the  Kadapah  system,  which,  according  to  Vreden- 
burg,  is  made  up  of  several  series  separated  from  one  another  by  unconformities.  The 
Lower  Kadapah  is  of  Proterozoic  age  and  the  Upper  Kadapah  is  certainly  older  than  the 
Siluric  and  probably  even  than  the  Cambric.  In  the  Upper  Kadapah  occur  “remarkable 
conglomerates  or  rather  boulder-beds  consisting  of  pebbles  of  various  sizes,  some  of  them 
very  large,  scattered  through  a  fine-grained  slaty  or  shaly  matrix.  *  *  *  These  peculiar 

boulder-beds  are  regarded  as  glacial  in  origin”  (1907:  20). 

In  Simla  occurs  the  Blaini  formation,  also  with  boulder-beds,  the  age  of  which,  according 
to  Holland  (see  in  David:  447)  is  certainly  older  than  the  Permic  and  possibly  of  late 
Proterozoic  time.  It  is  “a  conglomeratic  slate  composed  of  rounded  pebbles  of  quartz, 
ranging  up  to  the  size  of  a  hen’s  egg,  or  in  other  cases  angular  and  subangular  fragments 
of  slate  and  quartzite,  of  all  sizes  up  to  some  feet  across,  which  are  scattered  at  intervals 
through  a  fine-grained  matrix”  (447).  Holland  regards  these  beds  as  “almost  certainly  of 
glacial  origin”  (448).  They  may  eventually  be  shown  to  be  of  late  Proterozoic  age. 

Africa. — In  Proterozoic  strata,  far  beneath  the  Table  Mountain  series  of  probably  late 
Siluric  or  early  Devonic  age,  is  the  Griquatown  or  Pretoria  series  (29°  S.  lat.),  in  which 
glacial  materials  have  been  found.  At  present  no  definite  age  in  the  Proterozoic  era  can  be 
assigned  this  formation,  nor  can  it  be  said  that  the  glacial  horizon  is  either  that  of  the  Lower 
Huronian  or  of  the  latest  Proterozoic  time.  These  are  described  by  Schwarz  as  follows: 


“The  Griquatown  beds  are  a  highly  ferruginous  series  of  shales  and  slates.  *  *  *  Near 
the  top  of  the  series,  in  the  district  of  Hay,  west  of  Kimberly,  there  is  a  well-developed  glacial 
till,  the  matrix  now  converted  into  a  red  jasper;  yet  the  bowlders  of  chert,  when  weathered  out, 
show  the  unmistakable  facetting  and  scratching  which  can  have  been  caused  only  by  glacial 
action.  *  *  *  The  size  of  the  bowlders  varies  up  to  2  feet,  and  they  are  scattered  at  random 

through  the  matrix,  to  which  they  bear  a  very  small  proportion  in  regard  to  bulk.  *  *  *  j 

have  found  them  in  large  numbers  in  some  of  the  Witwatersrand  conglomerates.  The  whole 
thickness  of  the  glacial  till  is  probably  under  100  feet,  but  the  extent  of  country  covered  by  it 
in  the  area  already  mapped  is  over  1,000  square  miles”  (1906:  686). 


China. — In  the  provinces  of  the  middle  Yangtse  River  of  China  (110°  E.  long,  and 
31°  N.  lat.)  Willis  and  Blackwelder  (1907:  264-9;  1909:  39-40)  found  resting  uncon- 
formably  upon  very  ancient  granite  and  gneiss  a  series  of  quartzites  followed  by  at  least 
120  feet  of  an  unmistakable  glacial  tillite  (in  places  nearly  500  feet  thick),  green  in  color, 
which  is  in  turn  overlain  by  unfossiliferous  limestones  over  4,000  feet  thick.  This  lime¬ 
stone  Willis  correlates  with  the  fossiliferous  Middle  Cambric  occurring  100  miles  away. 


*  A.  C.  Lane  and  A.  E.  Seaman,  Jour.  Geol.,  15,  1907:  688. 


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THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


and  the  tillite  beneath  it  is  thought  to  have  formed  “close  to  sea-level.”  The  age  of 
these  tillites  is  conceded  to  be  at  least  as  old  as  the  Lower  Cambric,  but  when  we  note  that 
the  tillite  changes  quickly  into  the  overlying  limestone  within  a  few  feet  of  thickness, 
indicating  a  probable  break  in  sedimentation  between  the  two  series  of  deposits,  and  the 
further  fact  that  the  overlying  limestones  have  yielded  no  fossils,  we  see  that  these  glacial 
deposits  are  as  yet  unplaced  in  the  geologic  column.  Professor  Iddings  restudied  these 
tillites  in  1909,  and  he  likewise  could  find  no  fossils  in  the  limestone.  For  the  present  the 
tillites  are  referred  to  the  Proterozoic.  What  their  distribution  has  been  in  China  is  as 
yet  unknown.  (For  further  detail  by  Willis,  Blackwelder,  and  Iddings,  see  pp.  293-5.) 

Scotland. — In  the  northwest  of  Scotland  are  seen  some  of  the  oldest  rocks  known  to  the 
geologists  of  Europe.  The  basement  formations  make  up  the  Lewisian  series,  comparable 
to  the  Laurentian  of  American  geologists.  Upon  these  old  gneisses  and  schists,  mainly 
of  igneous  origin,  reposes  unconformably  a  great  pile  of  dull  red  sandstones,  shales,  and 
conglomerates,  referred  to  as  the  Torridonian,  that  Peach  states  were  laid  down  “under 
desert  or  continental  conditions”  (1912;  50).  These  attain  a  thickness  of  at  least  8,000 
to  14,000  feet,  and  are  in  turn  overlain  unconformably  by  Lower  Cambric  strata  having 
the  trilobite  Olenellus  and  related  genera.  The  Torridonian  was  laid  down  in  part  upon  a 
mountainous  topography  of  Lewisian  domes  strikingly  suggestive  of  glacial  erosion. 

In  western  Sutherland  and  Ross,  Geikie  states  that  the  observant  traveler  must  be 
struck  by  the  “extraordinary  contour  presented  by  the  gneiss.  A  very  slight  examination 
shows  that  every  dome  and  boss  of  rock  is  ice-worn.  The  smoothed,  polished,  and  striated 
surface  left  by  the  ice  of  the  glacial  period  is  everywhere  to  be  recognized.  Each  hummock 
of  gneiss  is  a  more  or  less  perfect  roche  moutonnee.  Perched  blocks  are  strewn  over  the 
ground  by  thousands.  In  short,  there  can  hardly  be  anywhere  else  in  Britain  a  more 
thoroughly  typical  piece  of  glaciation”  (1880;  401-3). 

Over  this  eroded  and  smoothed  ground  was  formed  a  coarse  reddish  breccia  with  many 
of  the  stones  decidedly  angular  and  “sometimes  stuck  on  end  in  the  mass.”  Some  blocks 
are  “fully  5  feet  long”  but  none  were  found  to  be  scratched  or  striated.  The  breccia  “is 
quite  comparable  to  moraine-stuff.”  The  material  came  from  a  land  that  lay  to  the 
northwest  and  that  has  since  sunk  into  the  Atlantic. 

Geikie  as  late  as  1903  still  stands  by  these  conclusions,  for  he  says: 

“Sometimes,  indeed,  where  the  component  blocks  of  the  basal  Torridonian  conglomerates 
are  large  and  angular,  as  at  Gairlock,  they  remind  the  observer  of  the  stones  in  a  moraine  or  in 
boulder-clay”  (1903:  891). 

“Some  of  these  roches  moutonnees  in  N.  W.  Scotland  may  be  of  Palaeozoic  age  [now  classed  as 
Proterozoic]  and  the  Torridonian  breccias  which  cover  them  have  a  singularly  ‘glacial’  aspect” 
(1309). 

“The  resemblance  of  these  rocks  [Sparagmite]  to  the  Torridonian  series  of  Scotland  is  re¬ 
markably  close”  (899). 

EARLIEST  PROTEROZOIC  GLACIATION. 

Canada. — The  oldest  known  tillite  was  recently  described  by  Professor  Coleman  (see 
figure  89).  It  occurs  at  the  base  of  the  Lower  Huronian  in  the  so-called  “slate  conglomer¬ 
ate,”  and  therefore  near  the  base  of  the  geologic  column  accessible  to  geologists.  These 
conglomerates  are  found  “from  point  to  point  across  all  northern  Ontario,  a  distance  of 
nearly  800  miles  [now  placed  at  1,000  miles]  and  from  the  north  shore  of  Lake  Huron  in 
latitude  46°  to  Lake  Nipigon  in  latitude  50°  [now  placed  at  750  miles].”  “The  appearance 
of  these  so-called  slate  or  graywacke  conglomerates  is  closely  like  that  of  the  Dwyka 
bowlder  clays  of  Africa”  (1907:  189).  They  rest  on  various  formations  older  than  the 
Huronian,  an  “undulating  surface  of  low  hills  and  valleys,  the  conglomerate  often  more  or 
less  filling  in  these  valleys”  (191).  A  scratched  or  polished  underground  has  been  found  in 
three  places,  but  as  a  rule  such  are  not  seen  because  of  the  unfavorable  conditions  for  their 


CLIMATES  OF  GEOLOGIC  TIME. 


273 


display.  The  evidence  of  the  tillites  is  in  favor  of  the  view  that  glaciation  in  Huronian 
Canada  was  not  “the  work  of  merely  local  mountain  glaciers,”  but  rather  due  to  “the  pres¬ 
ence  of  ice  sheets  comparable  to  those  which  formed  the  Dwyka.  *  *  *  This  implies 
that  the  climates  of  the  earlier  parts  of  the  world’s  history  were  no  warmer  than  those  of 
later  times,  and  that  in  Lower  Huronian  times  the  earth’s  interior  heat  was  not  sufficient  to 
prevent  the  formation  of  a  great  ice-sheet  in  latitude  46°  ”  (192).  (For  further  detail 
see  pp.  295-6.) 

CLIMATIC  EVIDENCE  OF  THE  SEDIMENTS. 

During  the  past  ten  years  it  has  become  evident  that  the  color  of  the  delta  deposits  of 
geologic  time,  and  especially  that  of  continental  deposits,  is  to  be  connected  largely  with 
differences  in  climate.  This  evidence,  however,  is  as  yet  difficult  of  interpretation,  because 
the  climatic  factors  are  not  easily  separated  from  those  due  to  topographic  form.  All  that 
can  be  done  now  is  to  call  attention  to  the  marked  changes  in  sedimentation  from  the 
gray,  green,  blue,  and  black  colors  to  the  red  beds  which  are  so  often  also  associated  with 
coarser  materials.  Barrell  states : 

“The  changes  from  the  red  beds  of  the  Catskill  formation,  several  thousand  feet  in  thickness, 
to  the  gray  Pocono  sandstones  with  a  maximum  thickness  of  1,200  to  1,300  feet,  then  to  the 
sharply  contrasted  red  shales  and  sandstones  of  the  Mauch  Chunk,  3,000  feet  in  maximum 
thickness,  and  back  to  the  massive  white  conglomerates  of  the  Pottsville  conglomerate,  1,200 
feet  in  maximum  thickness,  followed  by  the  coal  measures,  are  all  the  result  of  increasingly  wide 
swings  of  the  climatic  pendulum  which  carried  the  world  from  Upper  Devonian  warmth  and 
semi-aridity  to  Upper  Carboniferous  coolness,  humidity,  and  glaciation”  (1908:  163). 

In  regard  to  the  significance  of  gray  to  black  formations  Barrell  states: 

“Where  a  whole  formation,  representing  an  ancient  floodplain  or  delta,  shows  in  its  un¬ 
weathered  portions  an  absence  throughout  of  the  colors  due  to  iron  oxide,  and  a  variable  presence 
of  carbon,  giving  grays  to  black,  the  inference  is  that  the  formation  accumulated  under  a  con¬ 
tinuously  rainy  climate  or  one  which  in  the  drier  season  was  sufficiently  cool  or  cold  to  prevent 
noteworthy  evaporation;  such  climates  as  exist  in  Ireland,  Iceland,  or  western  Alaska”  (294). 

On  the  other  hand,  the  red  colors  in  stratified  rocks  are  in  general  due  to  arid  and  warm 
conditions. 

“Turning  to  the  climatic  significance  of  red,  it  would  therefore  appear  both  from  theoretical 
considerations  and  geological  observations  that  the  chief  condition  for  the  formation  of  red  shales 
and  sandstones  is  merely  the  alternation  of  seasons  of  warmth  and  dryness  with  seasons  of  flood, 
by  means  of  which  hydration,  but  especially  oxidation  of  the  ferru^nous  material  in  the  flood- 
plain  deposits  is  accomplished.  *  *  *  The  annual  wetting,  drying,  and  oxidation  not  only 

decompose  the  original  iron  minerals,  but  completely  remove  all  traces  of  carbon.  If  this  con¬ 
clusion  be  correct,  red  shales  or  sandstones,  as  distinct  from  red  mud  and  sand,  may  originate 
under  intermittently  rainy,  subarid,  or  arid  climates  without  any  close  relation  to  temperature 
and  typically  as  fluvial  and  pluvial  deposits  upon  the  land,  though  to  a  limited  extent  as  fluviatile 
sediments  coming  to  rest  upon  the  bottom  of  the  shallow  sea.  The  origin  of  such  sediment  is 
most  favored  by  climates  which  are  hot  and  alternately  wet  and  dry  as  opposed  to  climates  which 
are  either  constantly  cool  or  constantly  wet  or  constantly  dry”  (292-3). 

Red  sandstones  and  sandy  shales  recur  at  many  horizons  in  the  American  Paleozoic 
strata  and  markedly  so  at  the  close  of  the  Ordovicic,  Siluric,  Devonic,  Lower  and  Upper 
Carbonic,  and  early  Permic.  The  eastern  Triassic  beds,  and  those  of  the  Rocky  Mountains, 
are  nearly  everywhere  red  throughout,  and  there  is  considerable  red  color  in  the  Lower 
Cretacic  (Morrison  and  Kootenay)  of  the  Great  Plains  area.  Then,  too,  there  are  many 
red  beds  in  the  Proterozoic  of  America  as  well  as  of  Europe.  Between  these  zones  of 
brilliant  strata  are  the  far  more  widely  distributed  ones  of  grays  and  darker  colors,  and 

19 


274 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


these  are  the  deposits  of  the  times  when  the  oceans  have  most  widely  transgressed  the  lands, 
and  therefore  the  times  of  greater  humidity.  The  maximum  of  continental  extension  falls 
in  with  red  deposits  and  more  or  less  arid  climates,  (See  curve  for  aridity  in  figure  90.) 

VOLCANIC  DUST  AS  A  CLIMATIC  FACTOR. 

As  these  pages  are  going  through  the  press  two  interesting  papers  on  the  subject  of 
volcanic  dust  as  a  climatic  factor  have  appeared.  These  articles,  which  are  by  W.  J. 
Humphreys,*  should  be  read  by  every  student  of  paleometeorology.  The  following 
are  the  conclusions  reached: 

[Volcanic  dust  in  the  upper  atmosphere  has  been  one  of]  “several  contributing  causes  of  cli¬ 
matic  change,  *  *  *  a  cause  that  during  historic  times  has  often  been  fitfully  operative,  and 
concerning  which  we  have  much  definite  information.  *  *  * 

“At  an  elevation  that  in  middle  latitudes  averages  about  11  kilometers  the  temperature  of  the 
atmosphere  becomes  substantially  constant,  or,  in  general,  ceases  appreciably  to  decrease  with 
increase  of  elevation,  this  is,  therefore,  the  upper  limit  of  distinct  vertical  convection  and  of  cloud 
formation.  Hence,  while  volcanic  or  other  dust  in  the  lower  or  cloud  region  of  the  atmosphere  is 
quickly  washed  out  by  snow  or  rain,  that  which  by  any  process  happens  to  get  into  the  upper  or 
isothermal  region  must  continue  to  drift  there  until  gravity  can  bring  it  down  to  the  level  of  passing 
storms.  In  other  words,  while  the  lower  atmosphere  is  quickly  cleared  of  any  given  supply  of  dust, 
the  isothermal  region  retains  such  dust  as  it  may  have  for  a  time  that  depends  upon  the  size  and 
density  of  the  individual  dust  particles  themselves,  or  upon  the  rate  of  fall.  *  *  *  Volcanic  dust 
once  in  the  upper  atmosphere  must  remain  in  it  for  many  months  and  be  drifted  out,  from  whatever 
origin,  into  a  thin  veil  covering  perhaps  the  entire  earth.  *  *  *  A  veil  of  volcanic  dust  must  produce 
an  inverse  green-house  effect,  and  if  long  continued,  should  perceptibly  lower  our  average  tem¬ 
perature.  Let  us  see  then  what  observational  evidence  we  have  on  the  effect  of  volcanic  dust  on 
insolation  intensity  and  average  temperatures. 

“Pyrheliometric  records  [show]  that  there  was  a  marked  decrease  in  the  insolation  intensity 
from  the  latter  part  of  1883  (the  year  this  kind  of  observation  was  begun)  to  and  including  1886, 
from  1888  to  1892,  and  during  1903.  There  has  also  been  a  similar  decrease  since  about  the  middle 
of  1912.  Now  all  these  decreases  of  insolation  intensity,  amounting  at  times  to  20  per  cent  of  the 
average  intensity,  followed  violent  volcanic  eruptions  that  filled  the  isothermal  region  with  a  great 
quantity  of  dust.  *  *  * 

“  It  appears  quite  certain  that  volcanic  dust  can  lower  the  average  temperature  of  the  earth  by 
an  amount  that  depends  upon  the  quantity  and  duration  of  the  dust,  and  that  it  repeatedly  has 
lowered  it  certainly  from  1°  F.  to  2°  F.  for  periods  of  from  a  few  months  to  fully  three  years.  Hence 
it  certainly  has  been  a  factor,  in  determining  our  past  climates,  and  presumably  may  often  be  a 
factor  in  the  production  of  our  future  climates.  Nor  does  it  require  any  great  volume  of  dust  to 
produce  a  marked  effect.  Thus  it  can  be  shown  by  a  simple  calculation  that  less  than  the  one 
thousandth  part  of  a  cubic  mile  of  rock  spread  uniformly  through  the  upper  atmosphere  as  volcanic 
dust  would  everywhere  decrease  the  average  intensity  of  insolation  received  at  the  surface  of  the 
earth  by  at  least  20  per  cent  and  therefore  would,  presumably,  if  long  continued,  decrease  our 
average  temperatures  bj'  several  degrees.  *  *  *  This  effect  has  been  clearly  traced  back  to  1750,  or 
to  the  time  of  the  earliest  reliable  records.  Hence  it  is  safe  to  say  that  such  a  relation  between 
volcanic  dust  in  the  upper  atmosphere  and  average  temperatures  of  the  lower  atmosphere  has 
always  obtained,  and  therefore  that  volcanic  dust  must  have  been  a  factor,  possibly  a  very  im¬ 
portant  one,  in  the  production  of  many,  perhaps  all,  past  climatic  changes”  (a:  366-71). 

“The  intensity  of  the  solar  radiation  at  the  surface  of  the  earth  depends  upon  not  only  the  dusti¬ 
ness  of  the  earth’s  atmosphere  but  also  upon  the  dustiness,  and  of  course  the  temperature,  of  the 
solar  atmosphere.  Obviously  dust  in  the  sun’s  envelope  must  more  or  less  shut  in  solar  radiation 
just  as  and  in  the  same  maimer  that  dust  in  the  earth’s  envelope  shuts  it  out.  Hence  it  follows 
that  when  this  dust  is  greatest,  other  things  being  equal,  the  output  of  solar  energy  will  be  least, 

*  A  summary  pa-per  appeared  first,  entitled  (a)  “Volcanic  Dust  as  a  Factor  in  the  Production  of  Climatic  Changes,” 
Jour.  Washington  Acad.  Sci.,  3,  1913;  365-71.  The  complete  article  is  (b)  “  Volcanic  Dust  and  Other  Factors 
in  the  Production  of  Climatic  Changes,  and  Their  Possible  Relation  to  Ice  Ages,”  Bull.  Mt.  Weather  Observ., 
Washington,  6,  Pt.  I,  1913,  1-34. 


CLIMATES  OF  GEOLOGIC  TIME. 


275 


and  that  when  the  dust  is  least,  other  things  being  equal,  the  output  of  energy  will  be  greatest.  Not 
only  may  the  intensity  of  the  emitted  radiation  vary  because  of  changes  in  the  transparency  of  the 
solar  atmosphere  but  also  because  of  any  variations  in  the  temperature  of  the  effective  solar  surface 
which,  it  would  seem,  might  well  be  hottest  when  most  agitated,  or  at  the  times  of  spot  maxima,  and 
coolest  when  most  quiescent,  or  at  the  times  of  spot  minima”  (b;  16). 

BIOLOGIC  EVIDENCE. 

In  the  previous  pages  there  has  been  presented  the  evidence  for  cold  climates  during 
geologic  time  as  furnished  by  the  presence  of  the  various  tillites.  This  presentation  has  also 
been  made  from  the  standpoint  of  discovery  of  the  tillites,  which  in  general  is  in  harmony 
with  geologic  chronology,  i.  e.,  the  youngest  tillites  were  the  first  to  be  observed,  while  the 
most  ancient  one  has  been  discovered  recently. 

Variability  of  climate  is  also  to  be  observed  in  the  succession  of  plants  and  animals  as 
recorded  in  the  fossils  of  the  sedimentary  rocks.  In  this  study  we  are  guided  by  the 
distribution  of  living  organisms  and  the  postulate  that  temperature  conditions  have  always 
operated  very  much  as  they  do  now  upon  the  living  things  of  the  land  and  waters.  In 
presenting  this  biologic  evidence  we  shall,  however,  begin  at  the  beginning  of  geologic  time 
and  trace  it  to  modern  days,  for  the  reason  that  fife  has  constantly  varied  and  evolved  from 
the  more  simple  to  the  more  complex  organisms. 

Proterozoic. — The  first  era  known  to  us  with  sedimentary  formations  that  are  not 
greatly  altered  is  the  Proterozoic,  a  time  of  enormous  duration,  so  long  indeed  that  some 
geologists  do  not  hesitate  to  say  that  it  endured  as  long  as  all  subsequent  time.  These  rocks 
are  best  known  and  occur  most  extensively  over  the  southern  half  of  the  great  area  of 
2,000,000  square  miles  covered  by  the  Canadian  shield.  There  were  at  least  four  cycles  of 
rock-making,  each  one  of  which,  in  the  area  just  north  of  the  Great  Lakes  and  the  St. 
Lawrence  River,  was  separated  from  the  next  by  a  period  of  mountain-making.  These 
mountains  were  domed  or  bathohthic  masses  of  vertical  uplift  due  to  vast  bodies  of  deep- 
seated  granitic  magmas  rising  beneath  and  into  the  sediments.  In  the  Grenville  area  of 
Canada,  Adams  and  Barlow  (1910)  tell  us  that  the  total  thickness  of  the  pre-Proterozoic 
rocks  alone  is  94,406  feet,  or  nearly  18  miles.  Of  this  vast  mass  more  than  half  (50,286  feet) 
is  either  pure  limestone,  magnesian  limestone,  or  dolomite,  and  single  beds  are  known  with  a 
thickness  of  1,500  feet.  Certainly  so  much  limestone  represents  not  only  a  vast  duration  of 
time  but  also  warm  waters  teeming  with  life,  almost  nothing  of  which  is  as  yet  known.  There 
is  further  evidence  of  life  in  the  widely  distributed  graphites,  carbon  derived  from  plants 
and  animals,  which  make  up  from  3  to  10  per  cent  by  weight  of  the  rocks  of  the  Adirondacks 
(Bastin,  1910).  The  graphite  occurs  in  beds  up  to  13  feet  thick,  and  at  Olonetz,  Finland, 
there  is  an  anthracite  bed  7  feet  thick. 

It  is  also  becoming  plain  that  there  was  in  the  Proterozoic  a  very  great  amount  of 
fresh-water  and  subaerial  deposits,  the  so-called  continental  deposits,  some  of  which  indicate 
arid  climates.  Because  of  the  apparent  dominance  of  continental  deposits  and  the  great 
scarcity  of  organic  remains  throughout  the  Proterozoic,  Walcott  has  called  this  time  the 
Lipalian  era  (1910:  14). 

We  have  seen  that  the  Proterozoic  began  with  a  glacial  period,  as  evidenced  by  the 
tillites  of  Canada,  but  that  this  frigid  condition  did  not  last  long  is  attested  by  the  younger 
Lower  Huronian  limestones  of  Steeprock  Lake,  Ontario,  having  a  thickness  of  from  500  to 
700  feet  and  replete  with  Archseocyathinse,  coral-like  animals  up  to  15  inches  in  diameter, 
and  forming  reef  limestones  several  feet  thick,  found  there  by  Lawson  and  described  by 
Walcott  (1912).  This  discovery  is  of  the  greatest  value,  and  opens  out  a  new  field  for 
paleontologic  endeavor  in  Proterozoic  strata  and  for  philosophic  speculation  as  to  the 
time  and  conditions  when  life  originated. 


276 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


We  have  also  seen  that  the  Proterozoic  closed  with  a  frigid  climate,  as  is  attested  by 
the  tillites  of  Australia,  Tasmania,  and  possibly  China,  while  the  other  glacial  deposits 
of  India,  Africa,  Norway,  and  Keweenaw  certainly  do  in  part  indicate  another  and  older 
period  of  cool  to  cold  world  chmates. 

Cambric. — Due  to  the  researches  of  many  paleontologists,  but  mainly  to  those  of 
Charles  D.  Walcott,  we  now  know  that  the  shallow-water  seas  of  Lower  Cambric  time 
abounded  in  a  varied  animal  life  that  was  fairly  uniform  the  world  over  in  its  faunal  develop¬ 
ment.  It  was  essentially  a  world  of  medusae,  annelids,  trilobites,  and  brachiopods,  animals 
either  devoid  of  skeletons  or  having  thin  and  nitrogenous  external  skeletons  with  a  limited 
amount  of  lime  salts.  The  “lime  habit”  came  in  dominantly  much  later,  in  fact,  not 
before  the  Upper  Cambric.  However,  that  the  seas  in  Lower  Cambric  time  had  an  abun¬ 
dance  of  usable  lime  salts  in  solution  is  attested  by  the  presence  of  many  Hyohthes,  small 
gastropods  and  brachiopods,  and  more  especially  by  the  great  number  of  ArchsBocyathinse, 
which  made  reefs  and  limestones  200  feet  thick  and  of  wide  distribution  in  Australia, 
Antarctica,  Cahfornia  (thick  limestones  near  the  base  of  the  Waucoba  section),  southern 
Labrador  (reefs  50  feet  thick),  and  to  a  smaller  extent  in  Nevada,  New  York,  Spain, 
Sardinia,  northern  Scotland,  and  Arctic  Siberia. 

With  an  abundance  of  limestone  and  reef-making  animals  of  world-wide  distribution 
in  the  Lower  Cambric,  we  must  conclude  that  the  climate  at  that  time  was  at  least  warm  and 
fairly  uniform  in  temperature  the  world  over.  We  therefore  see  the  force  of  a  statement 
made  to  the  writer  by  Walcott  some  years  ago,  in  a  letter,  that  “the  Lower  Cambrian  fauna 
and  sediments  were  those  of  a  relatively  mild  climate  uninfluenced  by  any  considerable 
extent  of  glacial  conditions,”  and  also  that  “the  glacial  climate  of  late  Proterozoic  time 
had  vanished  before  the  appearance  of  earliest  Cambrian  time.” 

Toward  the  close  of  Lower  Cambric  time  there  was  considerable  mountain-making, 
without  apparent  volcanic  activity,  going  on  all  along  eastern  North  America  and  to  a 
lesser  extent  in  western  Europe.  These  uplifts  seemingly  had  much  effect  upon  the  marine 
life,  for  the  Middle  Cambric  faunas  became  more  and  more  provincial  in  character  in 
comparison  with  the  earlier,  more  cosmopohtan  faunas  of  Lower  Cambric  time. 

The  Archseocyathinfe,  which  had  endured  since  earliest  Proterozoic  time,  now  van¬ 
ished,  and  their  extinction  is  suggestive  of  cooler  waters;  there  was,  however,  a  greater 
variety  of  invertebrate  forms,  more  lime-secreting  invertebrates,  and  far  more  widespread 
limestone  deposition  in  Middle  Cambric  time.  In  the  Upper  Cambric  the  brachiopods, 
gastropods,  cephalopods,  and  bivalve  crustaceans  were  abundantly  represented  by  thick- 
shelled  forms,  and  in  most  places  throughout  North  America  there  was  marked  deposition 
of  hmestones,  magnesian  limestones,  and  dolomites,  all  of  which  is  suggestive  of  warmer 
waters. 

Ordovicic  and  Siluric. — The  Ordovicic  seas  from  Texas  far  into  the  Arctic  regions  were 
dominated  by  limestone  deposits  and  a  great  profusion  of  marine  life  that  was  also  more 
highly  varied  than  that  of  any  earlier  time.  The  same  species  of  graptohtes,  brachiopods, 
bryozoans,  trilobites,  and  other  invertebrate  classes  had  a  very  wide  distribution,  all  of 
which  is  evidence  that  at  that  time  the  earth  had  mild  and  uniform  climates.  In  the 
Middle  Ordovicic  and  again  late  in  that  period  reef  corals  were  common  from  Alaska  to 
Oklahoma  and  Texas  (Vaughan,  1911). 

Toward  the  close  of  the  Ordovicic,  mountain-making  was  again  in  progress  throughout 
eastern  North  America  without  significant  volcanic  activity,  but  in  western  Europe, 
where  the  movements  were  less  marked,  volcanoes  were  more  plentiful.  The  seas  were 
then  almost  completely  withdrawn  from  the  continents,  and  yet  when  the  Siluric  waters 
again  transgressed  the  lands  we  find  not  only  the  same  great  profusion  and  variety  of  hfe 
as  before,  but  as  widely  extended  limestone  deposition.  The  evidence  is  again  that  of  mild 
and  uniform  climates.  We  can  therefore  say  that  the  temperatures  of  air  and  water  had 


CLIMATES  OF  GEOLOGIC  TIME. 


277 


been  mild  to  warm  throughout  the  world  since  the  beginning  of  Cambric  time;  that  there 
was  a  marked  increase  of  warmth  in  the  Upper  Cambric;  and  that  these  conditions  were 
maintained  throughout  the  Ordovicic  and  the  earlier  half  of  the  Siluric,  since  shallow- 
water  corals,  reef  limestones,  and  very  thick  dolomites  of  Siluric  time  are  as  common  in 
Arctic  America  as  in  the  lower  latitudes  of  the  United  States  or  Europe. 

The  Siluric  closed  with  an  epoch  of  sea  withdrawal  and  North  America  was  again  arid,  for 
now  red  shales,  gypsum,  thick  beds  of  salt,  and  great  flats  of  sun-cracked  water-limestone 
were  the  dominant  deposits  of  the  vanishing  seas.  The  marine  faunas  were  as  a  rule 
scant  and  the  individuals  generally  under  the  average  size.  In  North  America  no  marked 
mountain-making  was  in  progress,  but  all  along  western  Europe,  from  Ireland  and  Scotland 
across  Norway  into  far  Spitzbergen,  the  Caledonian  Mountains  were  rising.  In  eastern 
Maine  throughout  Middle  and  Upper  Siluric  time  there  were  active  volcanoes  of  the 
explosive  type,  for  here  occur  vast  deposits  of  ash. 

Deionic. — In  the  succeeding  Lower  Devonic  time  the  Caledonian  intermontane  valleys 
of  Scotland  and  north  to  at  least  southern  Norway  were  filling  with  the  Old  Red  sandstone 
deposits  of  a  more  or  less  arid  climate.  On  the  other  hand,  the  invading  seas  of  northern 
Europe  were  small  indeed,  and  their  deposits  essentially  sandstones  or  sandy  shales,  but 
in  southern  Europe  and  North  America,  where  the  invasions  were  also  small  and  restricted 
to  the  margin  of  the  continent,  the  deposits  were  either  limestones  or  calcareous  shales. 
The  hfe  of  these  waters  was  quite  different  from  that  of  the  earlier  and  Middle  Siluric,  and 
entire  stocks  had  been  blotted  out  in  later  Siluric  time,  as  is  seen  best  among  the  graptolites, 
crinids,  brachiopods,  and  trilobites,  while  new  ones  appeared,  as  the  goniatites,  dipnoans 
or  lung-fishes,  sharks,  and  the  terrible  armored  marine  lung-fishes,  the  arthrodires. 

From  this  evidence  we  may  conclude  that  the  early  Paleozoic  mild  climates  were 
considerably  reduced  in  temperature  toward  the  close  of  the  Siluric  and  that  even  local 
glaciation  may  have  been  present.  Refrigeration  may  have  been  greatest  in  the  southern 
hemisphere,  where  the  marine  formations  of  Devonic  time  are  coarse  in  character  and,  in 
Africa,  of  very  limited  extent.  Corals  were  scarce  or  absent  here,  and  in  South  Africa  the 
glacial  deposits  of  the  Table  Mountain  series  may  be  of  late  Siluric  age;  if  so,  they  harmonize 
with  the  Caledonian  period  of  mountain-making  in  the  northern  hemisphere.  Warmer 
conditions  again  prevailed  in  the  latter  hemisphere  early  in  Middle  Devonic  times,  for 
coral  reefs,  limestones,  and  a  highly  varied  marine  life  with  pteropod  accumulations  were  of 
wide  distribution.  On  Bear  Island  workable  coal  beds  were  laid  down  in  late  Devonic  time. 

Throughout  the  Devonic,  but  more  especially  in  the  Lower  and  Middle  Devonic,  the 
entire  area  of  the  New  England  States  and  the  Maritime  Provinces  of  Canada  was  in  the 
throes  of  mountain-making,  combined  with  a  great  deal  of  volcanic  activity.  At  the  same 
time,  many  volcanoes  were  active  throughout  western  Europe. 

Carbonic. — The  world- wide  warm- water  condition  of  the  late  Devonic  seas  of  the  nor¬ 
thern  hemisphere  was  continued  into  those  of  the  Lower  Carbonic.  These  latter  seas  were 
also  replete  with  a  varied  marine  life,  among  which  the  corals,  crinids,  blastids,  echinids, 
bryozoans,  brachiopods,  and  primitive  sharks  played  the  important  r61es.  Limestones  were 
abundant  and  with  the  corals  extended  from  the  United  States  into  Arctic  Alaska.  Reefs  of 
Syxingopora  are  reported  in  northern  Finland  at  67°  55'  N.,  46°  30'  E.,  on  Kanin  Pensinula 
(Ramsay).  Even  several  superposed  coal  beds,  and  up  to  4  feet  in  thickness  of  pure  coal,  of 
early  Lower  Carbonic  age,  occur  at  Cape  Lisburne,  overlain  by  Lower  Carbonic  limestones 
with  corals.  It  is  generally  held  that  the  world  climate  at  this  time  was  uniformly  mild  and 
the  many  hundred  kinds  of  primitive  sharks  lead  to  the  same  conclusion.  There  were  in  the 
American  Devonic  39  species  of  these  sharks,  in  the  Lower  Carbonic  not  less  than  288,  in  the 
Coal  Measures  55,  and  in  the  earliest  Permic  only  10.  They  had  no  enemies  other  than 
their  own  kind  to  fear,  and  as  the  same  rise  and  decline  occurred  also  in  Europe,  we  must 
ask  ourselves  what  was  the  cause  for  this  rapid  dying-out  of  the  ancient  sharks  during 


278 


THE  CLIMATIC  FACTOE  AS  ILLUSTKATED  IN  ARID  AMERICA. 


and  shortly  after  early  Coal  Measures  time.  With  the  sharks  also  vanished  most  of  the 
crinids,  but  otherwise  there  was  an  abundance  and  variety  of  marine  life  (wide  distribution 
of  large  foraminifers)  with  much  limestone  formation.  The  vanishing  of  the  sharks  does  not 
appear  therefore  to  have  been  due  solely  to  a  reduction  of  temperature,  but  may  have  been 
further  helped  by  the  oscillatory  condition  and  retreat  of  the  late  Lower  Carbonic  seas. 

Toward  the  close  of  the  Lower  Carbonic,  or  after  the  Culm  and  its  coals  of  western 
Europe  had  been  laid  down,  mountain  movements  on  a  great  scale  began  to  take  place  in 
central  Europe,  and  then  were  born  the  Paleozoic  Alps  of  that  continent.  These  mountains, 
Kayser  tells  us,  were  in  constant  motion  but  with  decreasing  intensity  throughout  the 
Upper  Carbonic,  culminating  in  “a  mighty  chain  of  folded  mountains.”  Toward  the 
close  of  the  Upper  Carbonic  began  the  rise  of  the  Urals,  which  was  finished  in  late  Permic 
time  when  the  Paleozoic  Alps  of  Europe  were  again  in  motion.  These  movements  are 
also  traceable  in  Armenia  and  others  are  known  in  central  and  eastern  Asia.  Likewise,  in 
America,  the  southern  Appalachians  were  in  movement  at  the  close  of  the  Lower  Carbonic, 
but  the  greatest  of  all  of  the  Upper  Carbonic  thrustings  began  to  take  place  at  the  close  of  the 
period  and  culminated  apparently  in  the  earlier  half  of  Permic  time,  when  the  entire  Appa¬ 
lachian  system  from  Newfoundland  to  Alabama,  and  the  Ouachita  Mountains,  extending 
through  Arkansas  and  Oklahoma,  arose  as  majestic  ranges  anywhere  from  3  to  4  miles  high. 

These  mountain-making  movements  of  long  duration  at  first  caused  the  oceans  to 
oscillate  frequently  back  and  forth  over  parts  of  the  continents,  and  great  brackish-water 
marshes  were  developed,  producing  the  greatest  marsh  floras  and  the  greatest  accumulations 
of  good  coals  that  the  world  has  had.  The  paleobotanists  White  and  Knowlton  tell  us 
that  the  climate  of  Upper  Carbonic  time  was  relatively  uniform  and  mild,  even  subtropical 
in  places,  accompanied  by  high  humidity  extending  to  or  into  the  polar  circles.  Plant 
associations  were  then  ‘‘able  to  pass  from  one  high  latitude  to  the  opposite  without  meeting 
an  efficient  climatic  obstruction  in  the  equatorial  region”  (1910:  760). 

The  marine  faunas  of  Upper  Carbonic  time  were  fairly  uniform  in  development,  and 
many  species  had  a  wide  distribution,  although  the  biotas  were  still  somewhat  provincial 
in  character.  Limestones  or  calcareous  shales  predominated.  The  large  Protozoa  of 
the  family  Fusulinidse  occurred  throughout  the  northern  hemisphere  and  less  widely  in 
South  America.  They  were  also  very  common  in  Spitzbergen.  Staff  and  Wedekind 
(1910)  state  that  the  Eusulinidae  occur  here  in  a  black  asphaltic  calcareous  rock,  i.  e.,  a 
sapropel  like  those  now  forming  in  marine  tropical  regions,  according  to  Potonie.  The 
water,  they  state,  was  shallow,  highly  charged  with  calcium  carbonate  and  of  a  tropical 
character,  or  at  the  very  least  not  cooler  than  that  of  the  present  Mediterranean.  The 
very  large  insects  of  the  Coal  Measures  tell  the  same  climatic  story,  for  Handlirsch  (1908: 
1152)  says  that  the  cockroaches  of  that  time  were  as  long  as  a  finger  and  the  libellids  as 
long  as  an  arm.  They  w'ere  '‘brutal  robbers”  and  scavengers  living  in  a  tropical  and 
subtropical  climate,  or  at  the  very  least  in  a  mild  climate  devoid  of  frosts.  We  therefore 
conclude  that  after  Middle  Devonic  time  the  climate  of  the  world  was  as  a  rule  uniformly 
warm  and  more  or  less  humid  and  that  it  remained  so  to  the  close  of  Upper  Carbonic  time. 

During  the  time  of  these  mild  and  humid  climates  vast  accumulations  of  carbon 
extracted  by  the  plants  out  of  the  atmosphere  were  being  stored  up  in  brackish  and  fresh¬ 
water  swamps,  and  even  greater  quantities  of  this  element  were  being  locked  up  in  the 
limestones  and  calcareous  shales  in  the  seas  and  oceans.  According  to  the  physico-chemist 
Arrhenius,  and  many  geologists  and  paleontologists,  so  much  loss  of  carbon  dioxide  and 
its  associated  water  vapor  from  the  air  must  have  thinned  the  latter  greatly  and  thus 
largely  reduced  the  atmospheric  blanket  and  retainer  of  the  sun’s  heat  rays.  Therefore 
they  hold  that  these  factors  alone  were  sufficient  to  have  brought  on  a  glacial  climate. 
It  may  be  that  this  theory  will  not  stand  the  test  of  time,  but  even  so  we  have  learned 
that  in  Carbonic  times  there  were  earth  movements  on  so  grand  a  scale  as  to  be  but  slightly 
inferior  to  those  of  the  late  Tertiary  that  were  followed  by  the  Pleistocene  glacial  climate. 


CLIMATES  OF  GEOLOGIC  TIME. 


279 


Permic.— Very  early  in  Permic  time  the  mild  climate  of  the  past  was  greatly  changed; 
the  evidence  is  now  overwhelming  that  throughout  the  southern  hemisphere  there  was  a 
glacial  period  seemingly  of  even  greater  extent  than  that  of  the  northern  hemisphere  during 
the  Pleistocene.  This  evidence  is  most  easily  seen  in  the  wide  distribution  of  the  tillites 
and  the  scratched  and  polished  grounds  over  which  the  land  ice  moved  in  Africa,  Australia, 
Tasmania,  India,  and  South  America.  In  the  northern  hemisphere  the  evidence  of  ice 
work  is  far  less  marked;  but  tillites  occur  near  Boston,  Massachusetts,  and  in  the  Urals, 
and  there  is  much  evidence  of  thin  and  arid  climates,  seen  in  the  widely  distributed  red 
formations.  Then,  too,  the  land  life  of  this  time  clearly  indicates  that  a  great  climatic 
change  had  taken  place  in  the  environment  of  the  organic  world. 

The  grand  cosmopolitan  swamp  floras  of  the  Upper  Carbonic,  consisting  in  the  main  of 
spore-bearing  plants,  such  as  the  horse-tails  (Equisetales),  the  running  pines,  and  club- 
mosses  (Lycopodiales),  and  the  ferns,  among  which  were  also  many  broad-leaved  evergreens 
(Cordaites)  and  seed-bearing  ferns  (Cycadofihces),  were  very  largely  exterminated  in  the 
southern  hemisphere  at  the  beginning  of  Permic  time.  In  the  northern  hemisphere, 
however,  the  older  flora  maintained  itself  for  a  while  longer,  as  best  seen  in  North  America, 
but  finally  the  full  effects  of  the  cooled  and  glacial  clim.ates  were  felt  everywhere.  Then 
in  later  Permic  time  the  old  floras  completely  vanished,  except  the  hardier  pecopterids, 
cycads,  and  conifers  of  the  northern  hemisphere,  and  with  these  latter  mingled  the  migrants 
from  the  hardy  Gangamopteris  flora  originating  in  the  glacial  chmate  of  the  southern 
hemisphere  (White,  1907).  Some  of  the  trees  show  distinct  annual  growth  rings,  and  hence 
the  presence  of  winters.  It  was  these  woody  floras  that  gave  rise  to  the  cosmopolitan  floras 
of  early  Mesozoic  time. 

With  the  vanishing  of  the  cosmopolitan  coal  floras  also  went  nearly  all  of  the  Paleozoic 
insect  world  of  large  size  and  direct  development,  for  the  insects  of  late  Permic  time  were 
small  and  prophetic  of  modern  forms.  Then,  too,  they  all  passed  through  a  metamorphic 
stage  indicating,  according  to  Handlirsch,  that  the  insects  of  earlier  Permic  time  had 
learned  how  to  hibernate  through  the  winters  in  the  newly  originated  larval  conditions. 

Our  knowledge  of  the  land  vertebrates  of  late  Paleozoic  time  is  increasing  rapidly  and 
it  is  becoming  plainer  that  great  changes  were  also  in  progress  here.  The  vertebrates  of 
the  Coal  Measures,  either  the  armored  amphibians  (Stegocephalia)  or  the  primitive  reptiles, 
were  still  largely  addicted  to  the  “water  habit”  and  lived  in  fresh  waters  or  swamps,  but 
this  was  much  changed  by  the  arid  climates  and  vanishing  swamps  of  later  Permic  times, 
and  in  the  Triassic  we  meet  with  the  first  truly  terrestrial  reptilian  faunas. 

A  climatic  change  naturally  must  affect  the  land  life  more  quickly  and  profoundly  than 
that  of  the  marine  waters,  for  the  oceanic  areas  have  stored  in  themselves  a  vast  amount 
of  warmth  that  is  carried  everywhere  by  the  currents.  The  temperature  of  the  ocean  is 
more  or  less  altered  by  the  changes  of  climate,  be  they  of  latitude  or  of  glaciation.  The  sur¬ 
face  temperatures  in  the  temperate  and  tropical  regions,  however,  are  the  last  to  be  affected, 
and  only  change  when  all  of  the  oceanic  deeps  have  been  filled  with  the  sinking  cold  waters 
brought  there  by  the  currents  flowing  from  the  glaciated  area.  We  therefore  find  that  the 
marine  life  of  earlier  Permic  time  was  very  much  like  that  of  the  Coal  Measures,  and  that 
it  was  not  profoundly  altered  even  in  the  temperate  zones  of  Middle  Permic  time  (Zechstein 
and  Salt  Range  faunas) .  Our  knowledge  of  Upper  Permic  marine  Hfe  is  as  yet  very  limited 
and  will  probably  always  remain  so  because  of  the  world-wide  subtraction  of  the  seas  from 
the  lands  at  that  time.  It  was  a  period  of  continued  arid  climates,  and  the  marginal 
shallow  sea  pans  were,  as  a  rule,  depositing  red  formations  with  gj^sum,  and  locally,  as  in 
northern  Germany,  alternations  of  salt  with  anhydrite  or  polyhalite  in  thicknesses  up  to  3,395 
feet.  In  certain  of  these  zones  there  were  developed  annual  rings  so  regular  in  sequence 
as  to  lead  to  the  inference  that  they  were  the  depositions  of  warm  summers  and  cold  winters, 
enduring  for  at  least  5,653  years  (Gorgey,  1911). 


280 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


Triassic. — When  we  examine  into  the  Triassic  faunas  we  meet  at  once  with  a  wholly  new 
marine  assemblage.  The  late  Paleozoic  world  of  fusulinids,  tetracorals,  crinids,  brachi- 
opods,  nautilids,  and  trilobites  had  either  vanished  or  was  represented  by  a  few  small  and 
rare  forms.  On  the  other  side,  in  the  Triassic,  their  places  were  taken  by  a  rising  marine 
world  of  small  invertebrates,  now  hexacorals,  regular  echinids,  modern  bivalves  (among 
them  the  oysters),  siphonate  gastropods,  and  more  especially  by  a  host  of  ammonites  and  a 
prophecy  of  the  coming  of  squids  and  marine  reptiles.  Truly,  there  is  no  greater  change 
recorded  in  all  Historical  Geology! 

Plants  are  scarce  in  the  rocks  of  Triassic  time  until  near  its  close  in  the  Rhsetic,  when 
we  can  again  truly  speak  of  Triassic  floras.  These  are  known  from  many  parts  of  the 
world,  and  according  to  Knowlton  there  is  nothing  in  the  floras  to  suggest  a  “depau¬ 
perate  and  pinched”  condition,  as  has  often  been  said.  “In  North  Carolina,  Virginia 
and  Arizona,  there  are  trunks  of  trees  preserved,  some  of  which  are  8  feet  in  diameter 
and  at  least  120  feet  long,  while  hundreds  are  from  2  to  4  feet  in  diameter.  Many  of  the 
ferns  [some  are  tree  ferns]  are  of  large  size,  indicating  luxuriant  growth,  while  Equisetum 
stems  4  to  5  inches  in  diameter  are  only  approached  by  a  single  living  South  American 
species.  *  *  *  The  complete,  or  nearly  complete  absence  of  rings  in  the  tree  trunks 
indicates  that  there  were  no,  or  but  slight,  seasonal  changes  due  to  alterations  of  hot  and 
cold,  or  wet  and  dry  periods.”  On  the  whole,  the  climate  was  “warm,  probably  at  least 
subtropical”  (1910a;  200-2). 

Of  insects,  too  few  species  (27)  are  known  to  be  of  value  for  climatic  deductions.  On 
the  other  hand,  the  reptilian  life  of  the  Triassic  in  America,  Africa,  and  Europe  was  highly 
varied,  and  with  the  dinosaurs  dominant  and  often  of  large  size  again  gives  evidence  that 
appears  to  be  indicative  of  uniform  and  mild  climate. 

The  marine  Triassic  deposits  consisted  largely  of  thick  limestones,  and  such  are  well 
developed  in  Arctic  America  and  Arctic  Siberia.  One  of  the  oldest  faunas,  known  as  the 
Meekoceras  fauna,  has  a  very  great  distribution  from  Spitzbergen  to  India  and  Madagascar, 
and  from  Siberia  at  Vladivostok  to  California  and  Idaho.  In  general,  however,  the  Tri¬ 
assic  assemblages  were  more  provincial,  and  it  was  not  until  middle  and  late  Triassic  time 
that  the  faunas  again  had  wide  distribution.  Limestones  with  thick  coral  reefs,  of  the 
same  age,  appear  in  the  Alps  (up  to  1,000  meters  thick),  India,  California,  Nevada,  Oregon, 
and  Arctic  Alaska.  Smith,  from  whom  most  of  these  facts  were  taken,  states  that  this 
shows  there  was  during  the  Triassic  “nearly  uniform  distribution  of  warm  water  over  a 
great  part  of  the  globe”  (1912a:  397-8). 

We  may  therefore  conclude  that  the  rigid  climate  of  the  Permic  had  vanished  even 
before  the  earliest  of  Triassic  times,  and  that  the  climate  of  the  latter  period  until  near  its 
close  was  again  mild  and  fairly  uniform  though  semiarid  or  even  arid  the  world  over. 

Late  Triassic-Lias. — Throughout  much  of  late  Triassic  time  there  was  renewed  crustal 
instability,  for  we  have  the  evidence  of  volcanism  on  a  great  scale  all  along  the  Pacific  from 
central  California  into  far  Alaska,  in  eastern  North  America  from  Nova  Scotia  to  Virginia, 
in  Mexico,  South  America  (in  southern  Brazil  600  meters  thick),  and  New  Zealand.  The 
volcanoes  of  western  North  America  were  probably  insular  in  position,  for  their  lavas  and  ash 
beds  are  found  interbedded  with  marine  sediments.  Just  how  important  this  movement 
was  and  what  effect  it  had  upon  the  climate  is  not  yet  clear,  but  there  is  important  organic 
evidence  leading  to  the  belief  that  the  temperature  was  considerably  reduced  during  latest 
Triassic  and  earliest  Jurassic  time. 

Pompeckj,  Buckman,  and  Smith  state  that  late  Triassic  time  was  a  particularly  critical 
one  for  the  ammonites.  Of  the  far  more  than  1,000  known  species  of  Triassic  ammonites, 
not  one  passed  over  into  the  Jurassic,  and  but  a  single  family  survived  this  time,  the  Phyl- 
loceratidffi.  Pompeckj  says  that  “out  of  Phylloceras  has  developed  the  abundance  of 
Jurassic-Cretaceous  ammonites”  (1910:  64),  while  Buckman  holds  it  was  out  of  Nannites 
by  way  of  the  Liassic  Cymbites  that  the  later  fullness  of  ammonite  development  came. 


CLIMATES  OF  GEOLOGIC  TIME. 


281 


In  the  Liassic  there  are  now  known  415  species  of  insects  that  remind  one  much  of 
modern  forms.  Nearly  all  were  dwarf  species,  smaller  than  similar  living  insects  of  the  same 
latitude  and  far  smaller  than  Paleozoic  or  Upper  Jurassic  insects.  Handlirsch  (1910b) 
is  positive  that  this  uniform  dwarfing  of  the  Liassic  insects  was  due  to  a  general  reduction 
of  the  climate  and  that  the  temperature  was  then  cool  and  like  that  of  present  northern 
Europe  between  latitudes  46°  and  55°.  The  climate,  he  states,  was  certainly  cooler  than 
either  that  of  the  Middle  Triassic  or  Upper  Jurassic. 

In  this  connection  we  must  not  overlook  the  fact  that  the  known  Liassic  insects  are  of 
wide  distribution,  for  172  species  are  known  from  England,  164  from  Mecklenburg,  northern 
Germany,  75  from  Switzerland,  and  2  from  upper  Austria.  With  this  depauperating  of 
the  insects  and  the  vanishing  of  the  late  Triassic  ammonites,  there  is  also  to  be  noted  a 
marked  quantitative  reduction  and  geographic  restriction  among  the  reef  corals  of  Liassic 
time  We  therefore  are  seemingly  warranted  in  concluding  that  the  cooling  of  the  climate 
in  late  Triassic  and  early  Jurassic  time  was  not  local  in  character,  but  was  rather  of  a 
general  nature.  Much  workable  coal  was  also  laid  down  in  Liassic  time,  not  only  in  Hun¬ 
gary  but  also  in  many  places  eastward  into  China  and  Japan.  In  addition,  the  many  black 
shales  of  this  time  furnished  further  evidence  of  cool  and  non- tropical  climates;  coal  and 
black  shales  are  so  general  in  occurrence  throughout  the  Liassic  rocks  that  the  time  is  often 
referred  to  as  the  Black  Jura.  Finally,  certain  Liassic  conglomerates  of  Scotland  have  been 
thought  by  some  to  be  of  glacial  origin  (J.  Geikie). 

Jurassic. — The  Jurassic  formations  of  Europe  are  so  rich  in  fossils  that  they  have 
been  the  classic  ground  on  which  many  paleontologists  and  stratigraphers  were  reared. 
From  the  studies  of  these  faunas  came  the  first  clear  ideas  of  climatic  zones  and  world 
paleogeographic  maps  through  the  work  of  the  great  Neumayr  of  Vienna.  As  the  result 
of  a  very  long  study  of  the  ammonites  and  their  geographic  distribution,  he  came  to  the 
conclusion  in  1883  that  the  earth  in  Jurassic  time  had  clearly  marked  equatorial,  temperate, 
and  cool  polar  climates,  agreeing  in  the  main  with  the  present  occurrence  of  the  same 
zones.  He  also  said  that  ‘Hhe  equator  and  poles  could  not  have  very  much  altered  their 
present  position  since  Jurassic  times.”  His  conclusions  were,  however,  assailed  by  many, 
and  while  no  one  has  greatly  altered  his  geographic  belts  of  ammonite  distribution,  still 
the  consensus  of  opinion  to-day  is  that  these  are  representative  rather  of  faunal  realms 
than  of  temperature  belts.  On  the  other  hand,  it  is  admitted  that  there  were  then  clearly 
marked  temperature  zones — that  is,  a  very  wide  medial  warm-water  area,  embracing  the 
present  equatorial  and  temperate  zones,  with  cooler  but  not  cold  water  in  the  polar  areas. 
That  the  oceanic  waters  of  Middle  and  (somewhat  less  so)  of  Upper  Jurassic  times  were 
warm  throughout  the  greater  part  of  the  world  is  seen  not  only  in  the  very  great  abundance 
of  marine  life — probably  not  less  than  15,000  species  are  known  in  the  Jurassic  but  also 
in  the  far  northern  distribution  of  many  ammonites,  reef  corals,  and  marine  saurians. 
The  Jurassic  often  abounds  in  reefs  made  by  sponges,  corals,  and  bryozoans.  Jurassic  corals 
occur  3,000  miles  north  of  their  present  habitats. 

The  Jurassic  floras  were  truly  cosmopolitan,  and  Knowlton  tells  us  that  of  the  North 
American  species,  excluding  the  cycad  trunks,  about  half  are  also  found  in  Japan,  Man¬ 
churia,  Siberia,  Spitzbergen,  Scandinavia,  or  England.  ‘‘What  is  even  more  remarkable, 
the  plants  found  in  Louis  Philippe  Land,  63°  S.,  are  practically  the  same  [both  generically 
and  specifically]  as  those  of  Yorkshire,  England.  *  *  *  The  presence  of  luxuriant  ferns, 
many  of  them  tree  ferns,  equisetums  of  large  size,  conifers,  the  descendants  of  which  are 
now  found  in  southern  lands,  all  point  to  a  moist,  warm,  probably  subtiopical  climate 
(1910a:  204-5).  The  insects  of  this  time  were  again  large  and  abundant,  indicating  a 

warm  climate — evidence  in  harmony  with  the  plants.  ,  u  t. 

At  the  close  of  the  Jurassic  the  Sierra  Nevadas  of  California  and  the  Humboldt  Ranges 
of  Nevada  were  elevated;  probably  also  the  Cascade  and  Klamath  Mountains  farther  north; 


282 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


but  this  disturbance  seemingly  had  no  marked  effect  upon  the  world’s  climate,  though 
there  was  a  considerable  retreat  of  the  seas  from  the  continents. 

Cretacic. — The  emergence  of  the  continents  at  the  close  of  the  Upper  Jurassic  gave 
rise  to  extensive  accumulations  of  fresh-water  deposits,  known  in  western  Europe  as  the 
Wealden,  and  in  the  Rocky  Mountain  area  of  North  America  as  the  Morrison.  These 
are  now  regarded  as  of  Lower  Cretacic  (more  accurately  Comanchic)  age.  Along  the 
Atlantic  border  of  the  United  States  occur  other  continental  deposits,  known  as  the  Poto¬ 
mac  formations,  in  the  upper  part  of  which  the  modern  floras  or  Angiosperms  make  their 
first  appearance.  Before  the  close  of  the  Lower  Cretacic  this  early  hardwood  forest  had 
spread  to  Alaska  and  Greenland,  where  elms,  oaks,  maples,  and  magnolias  occurred. 
Knowlton  concludes  from  this  evidence  that  the  climate  '‘was  certainly  much  milder  than 
at  the  present  time”  and  “was  at  least  what  we  would  now  call  warm  temperate”  (1910a: 
205-6).  It  was  therefore  a  climate  somewhat  cooler  than  that  of  the  Jurassic.  On  the 
other  hand,  the  Neocomian  series  of  King  Karl’s  Land  has  sihcified  wood,  the  trunks  of 
which,  according  to  Nathorst,  are  at  least  80  cm.  in  diameter  and  show  210  annular  rings. 
These  rings  are  far  better  developed  than  in  stems  of  the  same  age  found  in  Europe,  “which 
indicates  that  the  trees  lived  in  a  region  where  the  difference  between  the  seasons  was 
extremely  pronounced”  (1912:  339). 

At  this  time,  in  the  temperate  and  tropical  belts,  the  world  had  the  greatest  of  all  land 
animals,  the  dinosaurs,  reptiles  attaining  a  length  in  North  America  of  75  feet  or  more 
and  in  equatorial  German  East  Africa  of  probably  125  feet.  Their  bones  range  to  50° 
N.  latitude,  and  the  animals  must  have  lived  in  a  fairly  warm  and  moist  chmate. 

While  the  Lower  Cretacic  seas  were  prolific  in  life,  the  most  characteristic  shellfish 
of  southern  Europe,  the  Mediterranean  countries,  and  Mexico,  were  the  limestone-making 
rudistids,  large  ground-living  foraminifers  (Orbitolina),  and  reef  corals.  In  northern 
Europe  and  in  the  United  States  from  southern  Texas  to  Kansas,  nothing  of  these  warm- 
water  faunal  elements  is  known.  It  is  recognized  that  the  north  European  seas  had  Arctic 
connections  by  way  of  Scandinavia  and  Russia,  and  along  the  west  coast  of  North  America 
are  seen  many  other  boreal  migrants  as  far  south  as  California  and  even  Mexico.  These 
waters,  however,  were  not  cold.  The  same  geographic  distribution  prevailed  in  the  Upper 
Cretacic  of  Europe.  This  distribution  was  first  noted  in  Texas  by  Ferdinand  Roemer  in 
1852,  and  he  further  observed  that  “in  each  case  the  European  deposit  is  approximately  10° 
farther  north  than  its  American  analogue,  ”  and  concluded  “  that  the  differences  between 
the  northern  and  southern  facies  were  due  to  climate  and  that  the  climatic  relations  between 
the  two  sides  of  the  Atlantic  were  about  the  same  in  Cretaceous  time  as  they  are  now” 
(Stanton,  1910:  67).  Even  though  Roemer’s  conclusion  as  to  climatic  zones  was  founded 
on  erroneous  stratigraphic  correlations,  still  his  theory  has  long  been  looked  upon  favorably, 
but  in  1908  Go  than  showed  that  the  fossil  woods  of  the  late  Upper  Cretacic  of  central 
Germany  have  distinct  annual  rings,  while  those  of  Egypt  do  not  have  a  trace  of  them. 
The  late  Cretacic  woods  of  Spitzbergen  also  have  decided  growth  rings.  Berry  (1912)  states 
that  the  climate  of  Upper  Cretacic  time  was  far  more  uniform  than  now  and  that  there  was 
an  increase  of  warmth  southward,  Alabama  having  then  a  climate  that  was  subtropical 
or  even  tropical.  On  the  other  hand,  the  early  Upper  Cretacic  or  Cenomanian  flora  of 
Atane  in  western  Greenland,  according  to  Nathorst,  “is  particularly  rich  in  the  leaves  of 
Dicotyledonous  trees,  among  which  are  found  those  of  planes,  tulip  trees,  and  bread 
fruits,  the  last  mentioned  closely  resembling  those  of  the  bread-fruit  tree  (Artocarpus 
incisa)  of  the  islands  of  the  southern  seas”  (1912:  340). 

In  Middle  Cretacic  times  the  oceans  began  again  to  spread  over  the  continents  and  this 
transgression  of  the  seas  was  one  of  the  greatest  of  the  geologic  past.  It  is  interesting  to 
note  that  even  though  there  was  great  opportunity  for  expansive  evolution,  but  few  new 
marine  stocks  appeared  here,  and  it  was  rather  a  time  of  death  to  many  characteristic 


CLIMATES  OF  GEOLOGIC  TIME. 


283 


stocks.  This  well-known  fact  is  clearly  brought  out  by  Walther  in  his  interesting  book, 
“Geschichte  der  Erde  und  des  Lebens”  (1908),  in  Chapter  26,  entitled  ‘‘Cretaceous  time 
and  its  great  mortahty.”  Entire  stocks  of  specialized  forms  vanished,  just  as  did  other 
stocks  at  the  close  of  the  Paleozoic.  In  late  Cretacic  time  it  was  the  ammonites,  belemnites, 
the  rudistids  that  began  to  develop  in  great  numbers  in  the  Lower  Cretacic,  and  the  other 
thick-shelled  large  bivalves  (Inoceramus)  that  perished.  In  addition,  there  was  a  great 
reduction  among  the  reef  corals,  the  replacing  of  the  dominant  ganoids  by  the  teleosts  or 
bony  fishes,  and,  finally,  the  complete  dying  out  of  the  various  stocks  of  marine  saurians. 

On  the  land,  with  the  further  rise  of  the  Angiosperm  floras,  we  see  the  vanishing  of  the 
reptilian  dragons  known  as  pterodactyls,  and,  at  the  very  close  of  the  Cretacic,  the  last  of 
the  large  and  small  dinosaurs  and  the  birds  with  teeth.  “We  thus  see  the  reptiles  displaced 
from  the  seas  by  the  fishes;  on  the  land  they  are  restricted  by  the  rise  of  the  mammals,  in 
the  air  after  a  short  struggle  by  the  more  finely  organized  birds — in  short,  the  reptilian 
dominance  is  destroyed  with  the  end  of  the  Mesozoic  era,  in  which  entire  time  they  were 
the  characteristic  feature  (Koken,  1893:  436). 

The  Upper  Cretacic  was  therefore  a  time  of  great  mortality  among  animals,  “here 
sooner,  there  later;  although  numerous  relict  faunas  arc  preserved  for  a  time  and  last  into 
the  Cenozoic,  still  there  never  was  so  great  a  mortality  as  that  taking  place  toward  the 
close  of  the  Cretacic”  (Walther,  1908:  449). 

During  the  Upper  Cretacic,  but  more  especially  toward  the  close  of  the  period,  mountain¬ 
making  on  a  vast  scale  went  on,  along  with  exceptional  outpourings  of  lavas  and  ashes. 
These  movements,  though  of  less  intensity,  were  repeated  in  early  Tertiary  times,  and 
while  they  were  equaled  only  by  those  of  the  closing  period  of  the  Paleozoic,  they  were 
exceeded  by  the  crustal  deformation  of  late  Tertiary  time;  they  form  the  Laramide  revo¬ 
lution  of  Dana,  embracing  the  mountains  of  western  North  and  South  America  from 
Cape  Horn  to  Alaska  and  the  reelevation  of  the  Appalachian  and  Antillean  Mountains. 
Throughout  the  Eocene  in  the  Rocky  Mountains  there  were  many  volcanoes  throwing 
out  immense  quantities  of  ashes  in  which  is  entombed  a  remarkable  vertebrate  fauna. 
Then  in  late  Cretacic  time  in  peninsular  India  occurred  the  Deccan  lava  flows,  the  most 
stupendous  eruptions  known  to  geologists,  covering  an  area  of  200,000  square  miles,  in 
thickness  anywhere  up  to  a  mile  or  more. 

Although  there  were  these  great  crustal  movements  toward  the  close  of  the  Upper 
Cretacic,  nevertheless  they  seem  to  have  had  no  marked  effect  on  the  climates  of  the 
world,  for  nowhere  has  anyone  shown  the  presence  of  unmistakable  glacial  tills  of  this  age.* 
Then,  too,  the  floras  of  early  Tertiary  times  are  said  to  be  of  about  the  same  character  as 
those  of  the  late  Cretacic  and  they  indicate  that  the  climates  were  warm  with  slight 
latitudinal  variation,  so  slight  that  even  in  Greenland  and  Spitzbergen  the  early  Tertiary 
floras  were  those  of  a  moist  and  mild  climate. 

Tertiary. — We  have  seen  that  there  was  no  marked  climatic  change  in  the  time  from 
the  Cretacic  to  the  Eocene,  but  that  there  was  a  reduction  in  temperature  is  admitted  by 
paleobotanists  and  students  of  marine  life.  Berry  states  that  the  Middle  Eocene  floras  of 
Europe  “show  many  tropical  characters  absent  in  the  earlier  Eocene”  (1910:  205).  The 
Oligocene  marine  faunas  were  prolific  in  species,  and  the  largest  of  all  foraminifers,  the  num- 
mulites,  although  still  present  at  this  time,  had  their  widest  distribution  and  largest  species 
in  the  Middle  Eocene  and  especially  in  the  Tethyian  Sea  of  the  Old  World,  extending  from 
20°  S.  to  20°  N.  latitude  (Stromer,  1909:  42). 

In  Miocene  time  on  Spitzbergen  (Cape  Staratschin)  lived  the  swamp  cypress  (Taxodium 
distichum  miocenum) ,  a  leafy  sequoia,  pines  and  firs,  besides  various  hardwood  trees,  such 


’At  the  Princeton  meeting  of  the  Geological  Society  of  America,  December  29,  1913,  Professor  W.  W.  Atwood 
announced  the  discovery  of  a  tillite  about  90  feet  thick  m  ^e  San  Juan  Mountains 

The  age  of  these  glacial  deposits  is  somewhere  between  late  Cretacic  and  late  Eocene.  We  therefore  are  now  on 
the  road  to  finding  the  physical  evidence  of  a  reduced  climate  dunng  or  following  the  close  of  the  Laramide 
revolution. 


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THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


as  poplars,  birches,  beeches,  oaks,  elms,  magnolias,  limes,  and  maples.  The  swamp  cypress, 
Nathorst  says,  “formed  forests,  as  in  the  swamps  in  the  southern  portion  of  the  United 
States.  This  conclusion  is  also  confirmed  by  the  occurrence  of  the  remains  of  rather 
numerous  insects”  (1912:  341).  All  of  the  plants  mentioned  then  flourished  as  far  north 
as  79°  N.  latitude,  and  even  at  nearly  82°  in  Grinnell  Land.  This  is  evidence  that  in  early 
Miocene  time  the  climate  was  at  least  warm-temperate  in  Arctic  America. 

Again,  Dali  (1895)  states  that  in  Middle  Miocene  time  considerable  reduction  of  the 
climate  appeared,  for  the  Atlantic  Chesapeake  faunas  were  those  of  temperate  waters  and 
they  spread  southward  as  far  as  the  eastern  area  of  the  Gulf  of  Mexico.  Similar  conditions 
are  noted  by  the  same  conchologist  in  the  northern  Pacific  Ocean.  He  says: 

“The  conditions  indicated  by  the  faunas  of  the  post-Eocene  Tertiary  on  the  Pacific  Coast  from 
Oregon  northward  are  a  cool  temperate  climate  in  the  early  and  Middle  Miocene,  a  warming  up 
toward  the  end  of  the  Miocene  culminating  in  a  decidedly  more  warm-water  fauna  in  the  Pliocene, 
and  a  return  to  cold  if  not  practically  Arctic  temperatures  in  the  Pleistocene”  (1907:  457-8). 

The  Tertiary  was  an  era  of  extraordinary  crustal  movements,  finally  resulting  in  the 
greatest  mountain  chains  of  all  geologic  time.  These  movements  began  in  early  Eocene 
time  in  the  Rocky  Mountains  and  at  the  close  of  this  epoch  further  deformation  took  place 
in  the  Klamath  and  Coast  Ranges  of  Oregon  and  the  Santa  Cruz  Mountains  of  California. 
In  Europe  the  elevations  of  Tertiary  time  started  at  the  close  of  the  Eocene  in  the  Pyrenees, 
and  in  the  Miocene  the  entire  “Alpine  system”  was  in  elevation.  This  unrest  spread  at 
the  same  time  to  the  Caucasus,  Asia,  and  to  the  entire  Himalayan  region  of  highest  moun¬ 
tains  and  elevated  plateaus,  an  area  22°  of  latitude  in  width.  It  is  probable  that  all  of  the 
world’s  great  mountain  chains  were  more  or  less  reelevated  in  Miocene  and  Pliocene  times, 
resulting  in  the  present  abnormally  high  stand  of  the  continents  when  contrasted  with  the 
oceanic  mean  level. 

These  elevations  also  altered  the  continental  connections,  for  North  and  South  America 
were  reunited  in  Miocene  times,  and  western  Europe,  Greenland,  and  America  were  severed 
late  in  the  Tertiary  era,  the  exact  time  being  as  yet  not  clearly  established.  With  these 
great  changes  also  must  have  come  about  marked  alterations  in  the  oceanic  currents  and, 
as  a  consequence,  in  the  distribution  of  heat  and  moisture  over  vast  areas  of  the  nor¬ 
thern  Atlantic  lands.  It  is  admitted  by  all  paleontologists  that  the  marine  waters  of 
late  Pliocene  times  in  the  Arctic  region  were  cool,  and  the  widespread  glacial  tills  of  the 
northern  hemisphere  are  evidence  of  a  glacial  climate  of  var3dng  intensity  throughout 
Pleistocene  time. 

CONCLUSIONS. 

Our  studies  of  the  paleometeorology*  of  the  earth  are  summed  up  in  figure  90.  We 
have  seen  that  two  marked  glacial  periods  are  clearly  established.  The  one  best  known 
was  of  Pleistocene  time  and  the  other,  less  well  known  in  detail,  of  earliest  Permic 
time.  Both  were  world-wide  in  their  effects,  reducing  the  mean  temperatures  sufl&ciently 
to  allow  of  vast  accumulations  of  snow  and  ice,  not  only  at  high  altitudes,  but  even  more 
markedly  at  low  levels,  with  the  glaciers  in  many  places  attaining  the  sea.  We  also  learn 
that  the  continental  glaciers  of  Pleistocene  time  were  dominant  in  the  polar  regions, 
while  those  of  Permic  time  had  their  greatest  spread  from  20°  to  40°  south  of  the  present 
equator,  and  to  a  far  less  extent  between  20°  and  40°  in  the  other  hemisphere.  There  is 
also  some  evidence  of  glaciers  in  equatorial  Africa  in  Permic  time.  We  may  further  state 
that,  although  Pleistocene  glaciation  was  general  in  the  Arctic  region,  there  certainly  was 
none  at  this  pole  in  early  Permic  time,  because  of  the  widespread  and  abundant  marine 
faunas  that  are  not  markedlj’-  unlike  those  of  the  Upper  Carbonic;  as  for  the  south  pole, 
our  knowledge  of  pre-Pleistocene  glaciation  is  as  yet  a  blank. 

*11.  F.  Osborn,  Compte  Rendu,  Congres  Internat.  ZooL,  Berne,  1904,  1905:  88.  For  a  review  of  the  papers 

treating  of  paleometeorology,  see  M.  Semper,  Geol.  Rundschau,  I,  1910;  57-80. 


CLIMATES  OF  GEOLOGIC  TIME. 


285 


A  glacial  period  does  not  appear  to  remain  constantly  cold,  but  fluctuates  between  cold 
glacial  climates  and  warmer  interglacial  times  of  varying  duration.  During  the  Pleistocene 
there  were,  according  to  the  best  glaciologists,  at  least  three,  if  not  four,  such  warmer 
intervals.  The  Permic  glacial  period  also  had  its  warmer  times,  while  the  interbedded  red 
strata  of  the  Proterozoic  tillites  seem  to  point  to  the  same  variabihty.  It  is  this  decided 
temperature  fluctuation  during  the  glacial  periods  that  is  so  very  difficult  to  explain. 

In  addition  to  the  well-known  Pleistocene  and  Permic  glaciation,  there  is  rapidly 
accumulating  a  great  deal  of  evidence  to  the  effect  that  there  were  at  least  two  and  probably 
three  other  periods  of  widespread  glacial  climates.  All  of  these  were  geologically  very 
ancient,  earlier  than  the  Paleozoic;  in  fact,  one  was  at  or  near  the  close  of  Proterozoic  time. 


while  another  was  at  the  very  beginning  of  that  era  and  almost  at  the  beginning  of  earth 

history  as  known  to  geologists.  .  j  •  e 

The  oldest  of  all  glacial  materials  occurs  at  the  base  of  the  Lower  Huroman  and  is  of 
great  extent  in  Canada.  Seemingly  of  the  same  time  is  the  Torridonian  glacial  testimony 
of  northwest  Scotland.  The  Proterozoic  tillites  of  China  in  latitude  31  _N.  may  also  be 
of  this  time.  If  these  correlations  are  correct,  then  the  oldest  glacial  evidence  indicates 
that  a  greatly  cooled  climate  prevailed  near  the  very  beginning  of  the  known  geologic 

record  and  that  it  was  dominant  in  the  northern  hemisphere.  i  •  i  r  +  • 

Toward  or  at  the  close  of  the  Proterozoic  there  is  other  evidence  of  a  glacial  climate  m 
Australia,  Tasmania,  and  Norway.  These  occurrences  of  tfllites  he  immediately  beneath 
Lower  Cambric  fossiUferous  marine  strata  and  probably  are  of  pre-Cambnc  age. 

In  India  there  is  also  evidence  of  late  Proterozoic  tillites  m  two  widely  separated  places, 
and  it  may  be  that  the  inadequately  studied  Keweenawan  testimony  of  the  Lake  Superior 


286 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


region  is  of  this  time.  If  so,  these  occurrences  record  a  distribution  of  glacial  materials 
very  similar  to  that  of  Permic  time.  Again,  the  Proterozoic  tillites  of  Africa  are  clearly 
of  another  age,  so  that  there  is  evidence  of  at  least  three  periods  of  glaciation  previous  to 
the  Paleozoic. 

The  physical  evidence  of  former  glacial  climates  is  even  yet  not  exhausted,  for  the  Table 
Mountain  tillites  of  South  Africa  point  to  a  cold  chmate  that  apparently  occurred,  at  least 
locally,  late  in  Siluric  time.  Finally,  there  may  have  been  a  seventh  cool  period  in  early 
Jurassic  time  (Lias),  but  the  biologic  evidence  so  far  at  hand  indicates  that  it  was  the  least 
significant  among  the  seven  probable  cool  to  cold  climates  so  far  discovered  in  the  geologic 
record. 

The  data  at  hand  show  that  the  earth  since  the  beginning  of  geologic  history  has  peri¬ 
odically  undergone  more  or  less  widespread  glaciation  and  that  the  cold  climates  have 
been  of  short  geologic  duration.  So  far  as  known,  there  were  seven  periods  of  decided 
temperature  changes  and  of  these  at  least  four  were  glacial  climates.  The  greatest  intensity 
of  these  reduced  temperatures  varied  between  the  hemispheres,  for  in  earliest  Proterozoic 
and  Pleistocene  time  it  lay  in  the  northern,  while  in  late  Proterozoic  and  Permic  time  it 
was  more  equatorial  than  boreal.  The  three  other  probable  periods  of  cooled  cHmates  are 
as  yet  too  little  known  to  make  out  their  centers  of  greatest  intensity. 

Of  the  four  more  or  less  well-determined  glacial  periods,  at  least  three  (the  earhest 
Proterozoic,  Permic,  and  Pleistocene)  occurred  during  or  directly  after  times  of  intensive 
mountain-making,  while  the  fourth  (late  Proterozoic)  apparently  also  followed  a  period  of 
elevation.  The  Table  Mountain  tilhtes  of  South  Africa,  if  correctly  correlated,  fall  in  with 
the  time  of  the  making  of  the  great  Caledonian  Mountains  in  the  northern  hemisphere. 
On  the  other  hand,  the  very  marked  and  world-wide  mountain-making  period,  with 
decided  volcanic  activity,  during  late  Mesozoic  and  earliest  Eocene  times,  was  not  accom¬ 
panied  by  a  glacial  climate,  but  only  by  a  cooled  one.  The  cooled  period  of  the  Liassic  also 
followed  a  mountain-making  period,  that  of  late  Triassic  time.  We  may  therefore  state  that 
cooled  and  cold  climates,  as  a  rule,  occur  during  or  immediately  follow  periods  of  marked 
mountain-making — a  conclusion  also  arrived  at  independently  by  Ramsay  (1910:  27). 

Geologists  are  beginning  to  see  clearly  that  the  lands  have  been  periodically  flooded 
by  the  oceans,  and  the  times  of  maximum  submergence  and  emergence  of  the  continents 
since  earliest  Paleozoic  time  are  fairly  well  known.  The  two  marked  glacial  periods  since 
Cambric  time  (Permic  and  Pleistocene)  and  the  three  other  more  or  less  cooled  chmates 
(late  Siluric,  Liassic,  and  late  Cretacic)  all  fall  in  with  the  times  when  the  continents  were 
more  or  less  extensively  and  highly  emergent.  There  were  no  cold  chmates  when  the 
continents  were  flooded  by  the  oceans,  and  it  may  be  added  that  the  periods  of  widespread 
limestone-making  preceded  and  followed,  but  did  not  accompany,  the  reduced  climates. 
On  the  other  hand,  the  periods  of  greatest  coal-making  (Upper  Carbonic  and  Upper  Cre¬ 
tacic)  accompanied  the  time  of  greatest  continental  flooding  and  preceded  the  appearance 
of  cooled  climates. 

The  more  or  less  coarse  red  sediments  seen  at  many  horizons  of  the  geologic  column 
are  interpreted  as  the  deposits  of  variably  arid  climates,  or  those  that  are  alternately  wet 
and  dry.  In  the  Paleozoic  they  are  seen  more  often  at  the  close  of  the  periods  when  the 
seas  were  temporarily  withdrawn  and  the  lands  were  most  extensive.  These  red  deposits 
alternate  with  formations  that  are  either  wholly  marine  or  of  brackish-water  origin,  and 
in  the  latter  case  of  gray,  green,  blue,  or  black  color. 

Humphreys  has  shown  that  volcanic  dust  in  the  isothermal  region  of  the  earth’s  atmo¬ 
sphere  does  appreciably  reduce  the  temperature  at  the  surface  of  the  globe.  It  is  thought 
that  if  explosive  volcanoes  continued  active  through  a  more  or  less  long  geologic  time,  this 
factor  alone  would  bring  on,  or  largely  assist  in  bringing  on,  a  more  reduced  temperature 
or  even  a  glacial  climate.  If  then,  we  may  further  postulate  that  volcanic  activity  is 


CLIMATES  OF  GEOLOGIC  TIME. 


287 


most  marked  during  times  of  mountain-making,  e.,  during  the  “critical  periods”  at 
the  close  of  the  eras  and  the  less  violent  movements  at  the  close  of  the  periods,  we  should 
expect  ice  ages,  or  at  least  considerably  cooled  climates,  occurring  here  also.  Let  us  see 
how  the  facts  agree  with  this  hypothesis. 

Of  the  “critical  periods”  at  the  close  of  the  Paleozoic,  Mesozoic,  and  Cenozoic  eras, 
we  know  that  the  first  and  last  were  accompanied  by  glacial  climates,  but  the  Mesozoic, 
though  a  time  of  very  extensive  mountain-making  and  great  and  prolonged  volcanic 
activity  in  North  America,  did  not  close  with  a  glacial,  but  only  with  a  slightly  cooled  cli¬ 
mate.  Not  only  this,  but  we  find  that  volcanism  was  renewed  in  the  Cordilleras  of  North 
America  throughout  much  of  the  Eocene,  and  yet  there  was  developed  no  glacial  climate 
at  this  time.*  In  the  same  way  the  marked  temperature  reduction  at  the  close  of  the 
Cenozoic  in  the  Pleistocene  was  subsequent  to  the  Miocene  and  Pliocene  movements  of 
this  period  and  not  coincident  with  them,  while  that  of  the  Paleozoic  appears  to  fall  in  with 
the  rise  of  the  Urals  and  Appalachians,  though  but  little  volcanism  seems  to  have  accom¬ 
panied  the  movements  in  North  America.  It  should  also  be  said  that  equally  extensive 
movements  were  going  on  in  Europe  in  the  rise  of  the  European  Alps  during  the  geologic 
times  before  and  after  the  Permic  glaciation,  and  that  the  earlier  movements  did  not 
appreciably  affect  the  climate. 

Again,  there  was  decided  mountain-making  toward  the  close  of  the  Siluric  in  the  forma¬ 
tion  of  the  Caledonian  Mountains  all  along  western  Europe  from  Spitzbergen  to  Scotland, 
with  marked  volcanic  extrusions  during  the  Siluric  and  early  Devonic  in  Maine,  the 
Maritime  Provinces  of  Canada,  and  Europe.  Yet  we  have  no  glacial  climate  at  these 
times,  certainly  not  in  the  northern  hemisphere;  rather  it  seems  that  the  temperature  was 
mild  the  world  over.  It  is  possible,  however,  that  the  Table  Mountain  tillites  of  South 
Africa  may  coincide  with  this  time,  and  if  so  a  colder  temperature  affected  the  southern 
hemisphere  only  locally. 

On  the  other  hand,  the  “life  thermometer”  indicates  a  cooled  period  at  the  close  of  the 
Triassic  and  the  following  Liassic,  but  this  reduction  of  temperature,  again,  is  geologically 
subsequent  to,  rather  than  coincident  with  the  marked  volcanic  activity  of  the  Triassic 
in  many  widely  separated  places. 

Finally,  there  were  earth  movements  of  considerable  magnitude  at  the  close  of  theLower 
Cambric,  Ordovicic,  and  Jurassic  that  were  not  accompanied  by  glacial  climates.  At  all  of 
these  times  there  appears,  however,  to  have  been  a  drop  in  temperature,  slight  for  the  two 
first-mentioned  periods  and  more  marked  for  the  third  one,  for  here  we  find  in  the  austral 
region,  during  earliest  Cretacic  times,  winters  alternating  with  summers. 

We  may  therefore  conclude  that  volcanic  dust  in  the  isothermal  region  of  the  earth 
does  not  appear  to  be  a  primary  factor  in  bringing  on  glacial  climates.  On  the  other 
hand,  it  can  not  be  denied  that  such  periodically  formed  blankets  against  the  sun’s  radiation 
may  have  assisted  in  cooling  the  climates  during  some  of  the  periods  when  the  continents 
were  highly  emergent. 

It  has  long  been  known  that  during  times  of  intensive  mountain-making  and  more  or 
less  cooled  chmates  there  was  great  destruction  and  alteration  of  life.  The  first  effects 
of  the  environmental  changes  occurred  among  the  organisms  of  the  land,  while  the  climax 
of  alteration  among  the  marine  life  appeared  later.  This  is  especially  well  seen  in  the 
Permic  glaciation,  which  first  blotted  out  the  cosmopolitan  Upper  Carbonic  flora  ^nd  the 
insects,  while  the  life  of  the  sea  continued  without  marked  change  into  Middle  Permic  time. 
In  the  later  Permic,  in  the  northern  equatorial  waters  of  Tethys,  occurred  the  final  destruc¬ 
tion  of  many  stocks  that  had  long  dominated  the  Paleozoic  seas.  The  explanation  of  these 
facts  appears  to  be  that  on  the  lands  the  change  of  climate  takes  imrnediate  effect  on  the 
organisms,  while  in  the  oceans  a  longer  time  is  consumed  in  cooling  down  the  warm  and 


*  See  footnote,  page  283. 


288 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


equable  temperature  and  in  filling  all  the  basins  with  cold  water.  Accordingly  the  last 
regions  in  the  oceans  to  come  under  the  influence  of  glacial  climates  must  be  the  shallow 
waters  of  the  equatorial  area.  The  proof  of  this  conclusion  is  seen  in  that  the  last  stand 
made  by  the  marine  Paleozoic  world  is  recorded  in  the  deposits  of  Tethys,  the  great  Mediter¬ 
ranean  sea  of  Permic  time.  It  is  also  here  that  we  find  nearly  all  of  the  Paleozoic  shallow- 
water  hold-overs  in  the  succeeding  period,  the  Triassic. 

The  cooled  but  not  frigid  climate  that  followed  the  magnificent  mountain-making  at 
the  close  of  the  Cretacic  also  produced  striking  changes  in  the  organic  world.  These 
changes  were  less  marked  than  those  of  Permic  time  and  more  noticeable  among  the  land 
animals  than  those  of  the  marine  waters,  affecting  especially  the  over-specialized,  large, 
thick-shelled,  and  degenerate  stocks. 

Great  changes  were  again  produced  among  the  large  land  animals  of  the  world,  as 
well  as  among  those  of  the  polar  and  temperate  oceanic  waters,  by  the  glaciation  of  Pleisto¬ 
cene  time.  The  present  shallow  waters  of  the  equatorial  region  still  maintain  the  late 
Tertiary  faunas,  and  Africa  is  the  asylum  where  the  higher  Pliocene  land  animals  have 
been  preserved  into  our  time. 

What  the  effects  of  the  Proterozoic  glacial  climates  were  upon  the  living  world  of  that 
time  it  is  impossible  to  say,  because  we  have  as  yet  discovered  but  little  of  the  organic 
record.  The  apparently  sudden  appearance  of  life  at  the  base  of  the  Cambric  is  partially 
explained  by  the  widespread  absence  of  the  marine  Proterozoic  record,  an  era  during  which 
the  nuclear  portions  of  the  continents  appear  to  have  been  decidedly  emergent  for  a  very 
long  time. 

The  marine  “life  thermometer’’  indicates  vast  stretches  of  time  of  mild  to  warm  and 
equable  temperatures,  with  but  slight  zonal  differences  between  the  equator  and  the  poles. 
The  great  bulk  of  marine  fossils  are  those  of  the  shallow  seas,  and  the  evolutionary  changes 
recorded  in  these  “medals  of  creation”  are  slight  throughout  eternities  of  time  that  are 
punctuated  by  short  but  decisive  periods  of  cooled  waters  and  great  mortality,  followed  by 
quick  evolution,  and  the  rise  of  new  stocks.  The  times  of  less  warmth  are  the  miotherm 
and  those  of  greater  heat  the  pliotherm  periods  of  Ramsay  (1910:  15). 

On  the  land  the  story  of  the  chmatic  changes  is  different,  but  in  general  the  equability 
of  the  temperature  simulates  that  of  the  oceanic  areas.  In  other  words,  the  lands  also 
had  long-enduring  times  of  mild  to  warm  climates.  Into  the  problem  of  land  climates, 
however,  enter  other  factors  that  are  absent  in  the  oceanic  regions,  and  these  have  great 
influence  upon  the  climates  of  the  continents.  Most  important  of  these  is  the  periodic 
warm-water  inundation  of  the  continents  by  the  oceans,  causing  insular  climates  that  are 
milder  and  moister.  With  the  vanishing  of  the  floods  somewhat  cooler  and  certainly  drier 
climates  are  produced.  The  effects  of  these  periodic  floods  must  not  be  underestimated, 
for  the  North  American  continent  was  variably  submerged  at  least  seventeen  times,  and 
over  an  area  of  from  154,000  to  4,000,000  square  miles  (Schuchert,  1910:  601). 

When  to  these  factors  is  added  the  effect  upon  the  climate  caused  by  the  periodic 
rising  of  mountain  chains,  it  is  at  once  apparent  that  the  lands  must  have  had  constantly 
varying  climates.  In  general  the  temperature  fluctuations  seem  to  have  been  shght,  but 
geographically  the  climates  varied  between  mild  to  warm  pluvial,  and  mild  to  cool  arid. 
The  arid  factor  has  been  of  the  greatest  import  to  the  organic  world  of  the  lands.  Further, 
when  to  all  of  these  causes  is  added  the  fact  that  dming  emergent  periods  the  formerly 
isolated  lands  were  connected  by  land  bridges,  permitting  intermigration  of  the  land  floras 
and  faunas,  with  the  introduction  of  their  parasites  and  parasitic  diseases,*  we  learn  that 
while  the  chmatic  environment  is  of  fundamental  importance  it  is  not  the  only  cause 
for  the  more  rapid  evolution  of  terrestrial  hfe.  Unfortunately,  the  record  of  land  hfe, 

*This  subject  is  fully  discussed  by  R.  T.  Eccles,  m.d.,  in  the  following  papers:  “Parasitism  and  Natural  Selection,” 

“Importance  of  Disease  in  Plant  and  Animal  Evolution,”  “ The  Scope  of  Disease,”  and  “  Disease  and  Genetics.” 

Medical  Record  for  July  31,  1909;  March  16,  1912;  March  8,  and  August  2,  1913. 


CLIMATES  OF  GEOLOGIC  TIME. 


289 


and  ©specially  of  the  animal  world,  is  the  most  imperfect  of  all  paleontologic  records 
until  we  come  to  Tertiary  time.  The  known  mammal  history  is  a  vast  one  and,  although 
very  difficult  to  interpret  from  the  climatic  standpoint,  we  have  in  the  work  of  Deperet 
(1909)  and  Osborn  (1910)  glimpses  into  the  many  temperature  fluctuations,  faunal  isola¬ 
tions,  and  intercontinental  radiations  of  Tertiary  time.  The  history  of  the  Tertiary  is 
the  last  one  of  at  least  three  previous  and  similar  records  (Mesozoic,  later  and  earlier 
Paleozoic)  of  vastly  longer  eras,  taking  us  back  to  a  time  when  the  lands  were  without 
visible  life. 

In  conclusion,  it  is  seemingly  clear  that  the  variability  in  the  storage  of  solar  radiation 
by  the  earth’s  atmospheric  blanket  and  by  oceanic  waters,  and  the  consequent  climatic 
variations  of  the  past  and  present  are  due  in  the  main  to  topographic  changes  in  the 
earth’s  crust.  These  telluric  changes  alter  the  configuration  of  the  continents  and  oceans, 
the  air  currents  (moist  or  dry),  the  oceanic  currents  (warm,  mild,  or  cool),  and  the  volcanic 
ash-content  of  the  atmosphere. 

On  the  other  hand,  a  great  deal  has  been  written  about  the  supply  and  consumption 
of  the  carbonic  acid  of  the  air  as  the  primary  cause  for  the  storage  of  warmth  by  the 
atmospheric  blanket.  A  greater  supply  of  carbon  dioxide  is  said  to  cause  increase  of  tem¬ 
perature,  and  a  marked  subtraction  of  it  will  bring  on  a  glacial  climate.  This  aspect  of 
the  climatic  problem  is  altogether  too  large  and  important  to  be  entered  upon  here.  It  is 
permissible  to  state,  however,  that  the  glacial  climates  are  irregular  in  their  geologic 
appearance,  are  variable  latitudinally,  as  is  seen  in  the  geographic  distribution  of  the  tillites 
between  the  poles  and  the  equatorial  region,  and  finally  that  they  appear  in  geologic  time 
as  if  suddenly  introduced.  These  differences  do  not  seem  to  the  writer  to  be  conditioned 
in  the  main  by  a  greater  or  smaller  amount  of  carbon  dioxide  in  the  atmosphere,  for  if  this 
gas  is  so  strong  a  controlling  factor,  it  would  seem  that  at  least  the  glacial  climates  should 
not  be  of  such  quick  development.  On  the  other  hand,  an  enormous  amount  of  carbon 
dioxide  was  consumed  in  the  vast  limestones  and  coals  of  the  Cretacic,  with  no  glacial 
climate  as  a  result;  though  it  must  be  admitted  that  the  great  limestone  and  vaster  coal 
accumulations  of  the  Pennsylvanic  were  quickly  followed  by  the  Permic  glaciation.  Again 
it  may  be  stated  that  the  Pleistocene  cold  period  was  preceded  in  the  Miocene  and  Pliocene 
by  far  smaller  areas  of  known  accumulations  of  limestone  and  coal  than  during  either  the 
Pennsylvanic  or  Cretacic,  and  yet  a  severe  glacial  climate  followed. 

Briefly,  then,  we  may  conclude  that  the  markedly  varying  climates  of  the  past  seem  to 
be  due  primarily  to  periodic  changes  in  the  topographic  form  of  the  earth’s  surface,  plus 
variations  in  the  amount  of  heat  stored  by  the  oceans.  The  causation  for  the  warmer 
interglacial  chmates  is  the  most  difficult  of  all  to  explain,  and  it  is  here  that  factors  other 
than  those  mentioned  may  enter. 

Granting  all  this,  there  still  seems  to  lie  back  of  all  these  theories  a  greater  question 
connected  with  the  major  changes  in  paleometeorology.  This  is:  What  is  it  that  forces 
the  earth’s  topography  to  change  with  varying  intensity  at  irregularly  rhythmic  intervals? 
This  difficult  and  elusive  problem  the  older  geologists  solved  with  a  great  deal  of  assurance 
by  saying  that  such  change  was  due  to  a  cooling  earth,  resulting  in  periodic  shrinkage, 
but  the  amount  of  shrinkage  that  would  necessarily  have  taken  place  to  account  for  all 
the  wrinklings  and  overthrustings  of  the  earth’s  crust  during  geologic  time  would  be  fai 
greater  than  that  which  has  apparently  occurred.  Further,  a  cooling  earth  is  yet  to  be 
demonstrated.  Again,  some  paleogeographers  seem  to  see  a  periodic  heaping  up  of  the 
oceanic  waters  in  the  equatorial  region  and  a  pulsatory  flowing  away  later  toward  the  poles. 
If  these  observations  are  not  misleading,  are  we  not  forced  to  conclude  tha.t  the  earth  s 
shape  changes  periodically  in  response  to  gravitative  forces  that  alter  the  body-form. 


20 


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THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


SUPPLEMENTARY  NOTES  ON  GLACIATION  BEFORE  THE  PERMIC  PERIOD. 

PRE-DEVONIC  GLACIAL  DEPOSITS  OF  SOUTH  AFRICA. 

In  Cape  Colony,  South  Africa,  there  is  a  thick  marine  series  of  shales  and  sandstones  known  as 
the  Bokkeveld  series,  which  appears  to  be  of  late  Lower  Devonic  age.  In  western  and  southern 
Cape  Colony  it  is  everywhere  seen  to  lie  upon  the  Table  Mountain  series  of  wide  distribution 
and  with  evidence  of  a  glacial  climate.  The  actual  contact  of  these  two  series  of  strata  shows 
“no  signs  of  unconformity”  between  them,  but  in  the  places  “where  a  clean-cut  section  of  the 
junction  can  be  seen,”  as  “that  on  the  left  bank  of  the  Gamka  River  immediately  above  its 
great  Poort  through  the  Zwartebergen,  *  *  *  ‘the  end  of  the  white  sandstones  [of  the  Table 

Mountain  series]  and  the  beginning  of  the  blue-black  shales  of  the  Bokkeveld  is  so  sudden  and 
exact  that  one  can  place  a  knife  between  them  and  say  confidently  that  on  one  side  are  the  rocks 
of  the  Table  Mountain  series  and  on  the  other  those  of  the  Bokkeveld  series’  ”  (Rogers,  1905: 121). 
This  sharp  differentiation  of  the  Lower  Devonic  black  shales  from  the  white  sandstones  of  the 
Table  Mountain  series  seems  to  indicate  clearly  that  the  contact  is  a  disconformable  one  and 
that  the  sea  invaded  a  land  of  sandstones.  If  this  is  true,  the  section  is  broken  and  we  can  not 
therefore  positively  state  the  age  of  the  Table  Mountain  series — it  has  as  yet  yielded  no  fossils  of 
stratigraphic  value — other  than  that  it  is  older  than  Devonic,  but  how  much  older  is  still  to  be 
determined.  The  facts,  however,  that  the  rocks  older  than  the  Table  Mountain  series  are  far 
more  deformed  and  greatly  intruded  by  igneous  materials,  that  the  Table  Mountain  and  Bokke¬ 
veld  series  do  not  give  evidence  of  a  long  erosion  interval  between  them,  and  that  both  were 
deformed  together  subsequent  to  Bokkeveld  time,  seem  to  indicate  that  the  age  of  the  former  is 
rather  late  Siluric  than  early  Devonic.  The  further  fact  that  the  fossils  are  bivalves  and  gastro¬ 
pods  indicates  clearly  that  the  Table  Mountain  series  is  of  post-Cambric  deposition. 

Rogers  also  says: 

“The  Table  Mountain  series  is  remarkably  constant  in  lithological  characters  throughout 
its  extent.  The  maximum  thickness  is  about  5,000  feet,  and  of  this  more  than  4,000  feet  are 
sandstones  or  quartzites”  (107). 

“  The  whitish-grey  colour  of  so  much  of  the  sandstone  belonging  to  this  series  is  due  to  weather¬ 
ing.  At  a  distance  of  1  or  2  feet  from  the  outside  the  rock  is  usually  blue,  owing  to  a  small  quantity 
of  iron  in  the  state  of  ferrous  compounds”  (108). 

“A  very  frequent  characteristic  of  the  sandstones  of  this  group  is  the  occurrence  of  round 
pebbles  of  white  quartz  up  to  3  inches  in  diameter.  They  usually  occur  singly,  more  rarely  in 
thin  layers  a  few  feet  long  and  about  an  inch  thick.  The  pebbles  themselves  are  rarely  more 
than  an  inch  in  diameter.  It  is  rather  difficult  to  explain  the  frequence  of  isolated  pebbles  in  the 
sandstone  without  recourse  to  some  agency  that  lifted  pebbles  from  the  shore  and  dropped  them 
in  deeper  waters”  (109-10). 

“In  the  western  mountains  a  second  shale  band  is  found  about  1,000  feet  below  the  top  of  the 
series.  *  *  *  'pj^g  ^ost  interesting  point  about  the  Pakhuis  section  is  the  occurrence  of 

pebbles  up  to  5  inches  in  diameter  scattered  irregularly  through  the  shale  and  mudstone,  without 
any  tendency  to  form  beds  of  conglomerate.  Several  of  the  pebbles  have  been  found  to  be 
flattened  on  one  or  more  sides  and  deeply  striated  in  the  manner  characteristic  of  pebbles  that 
have  come  from  a  glaciated  region”  (111-12). 

“The  occurrence  of  flattened  and  striated  pebbles  scattered  at  intervals  through  a  fine-grained 
laminated  rock  is  very  strong  evidence  that  glacial  conditions  prevailed  on  the  land  whence  the  peb¬ 
bles  came,  and  that  these  pebbles  were  carried  away  from  the  land  by  floating  ice  and  dropped 
by  the  melting  of  the  ice  on  to  the  mud  being  deposited  at  the  bottom  of  the  water”  (113). 

“If  the  Table  Mountain  sandstone  is  regarded  as  an  ordinary  coarse  deposit  formed  in  either 
a  fresh-water  basin  or  the  sea,  the  land  from  which  the  material  was  washed  can  not  have  lain  far 
from  the  present  outcrops  of  the  rock.  The  only  evidence  of  the  closer  proximity  to  land  of  one 
part  of  the  sandstone  than  another  is  the  greater  development  of  conglomerates  on  the  west,  in 
the  Piquetberg  Division  and  the  Olifant’s  River  Mountains,  than  elsewhere.  There  is  no  such 
evidence  known  from  the  Bokkeveld  Mountain,  or  along  the  Zwartebergen,  or  the  south  coast. 
At  present,  then,  we  must  conclude  that  while  the  nature  of  the  rock  renders  it  probable  that  the 
Table  Mountain  series,  so  far  as  exposed  in  the  Colony,  was  formed  not  far  from  land,  and  that 
consequently  the  land  lay  more  or  less  parallel  to  the  present  distribution  of  the  series,  the  only 
definite  clue  to  the  position  of  any  part  of  that  land  is  to  be  found  in  the  conglomerates  of  the 
west”  (116-17). 


CLIMATES  OF  GEOLOGIC  TIME. 


291 


Hatch  and  Corstorphine  state: 

D  practically  unknown,  but  Griesbach  found  some  small  bivalves  and  a  finely  striated 

Patella,  both  too  indistinct  for  determination,  in  certain  shales,  which  he  considered  interbedded 
in  the  series  at  Kranz  Kop,  near  Greytown.  Anderson,  who  visited  the  locality,  during  the 
period  covered  by  his  first  report,  was  unsuccessful  in  his  search  for  additional  organic  remains  ” 
(1909:  77-8). 

From  an  earlier  paper  by  Rogers  and  Schwarz  the  following  is  gleaned: 

“Not  only  is  the  rock  similar  to  some  varieties  of  the  Dwyka  conglomerate  in  general  litho¬ 
logical  character,  and  in  being  what  we  may  call  a  conglomeratic  mudstone,  but  glaciated  pebbles 
occur  in  it.  *  *  *  The  pebbles  scattered  at  intervals  through  the  conglomeratic  mudstone  are 

of  all  sizes  up  to  5  inches  in  length.  They  consist  of  quartz,  quartzite,  grits,  slaty  rocks,  granite, 
and  felsite.  The  small,  whitish,  often  nearly  spherical  quartz  pebbles  found  in  this  rock  are 
also  very  characteristic  of  the  sandstone  above  and  below,  in  which  they  occur  isolated  and  in 
thin  beds  of  conglomerate.  We  picked  out  nine  pebbles  from  1)^  to  4  inches  in  length,  which 
have  the  characteristic  form  of  glaciated  stones,  that  is,  they  are  flattened  on  one  or  more  sides, 
and  the  flat  faces  show  scratches,  often  arranged  in  parallel  groups,  but  the  other  parts  of  the 
surface  are  also  sometimes  striated.  _  *  *  *  This  evidence,  then,  irresistibly  forces  us  to  the 

conclusion  that  in  South  Africa  during  the  time  of  the  deposition  of  the  Table  Mountain  sand¬ 
stone — that  is,  in  about  lower  Devonian  times — glacial  conditions  existed  somewhere  in  this 
neighbourhood.  We  had  no  opportunity  of  examining  the  shale-band  north  of  this,  but  to  the 
south,  ice-scratched  boulders  do  not  occur  in  it,  so  that  presumably  the  boulders  came  from  the 
north,  just  as  the  Dwyka  boulders  did”  (1901:  78-9). 


LATEST  PKOTEROZOIC  GLACIATION. 

Australia. — Below  the  great  tillite  zone  there  are  over  11,000  feet  (in  1912  Howchin  states  40,000 
to  50,000,  including  the  Cambric)  of  conglomerates,  grits,  thick  feldspathic  quartzites,  slates  and 
phyllites,  and  thin  and  thick  zones  of  limestone  resting  upon  an  ancient  complex  of  highly  de¬ 
formed  and  altered  rocks.  On  these  strata  rests  the  great  zone  of  tillite,  attaining  thicknesses 
ranging  from  592  to  about  1,500  feet.  Throughout  this  mass  of  material  no  recognizable  fossils 
are  as  yet  known  and  therefore  its  age  cannot  be  determined  other  than  that  it  is  older  than  the 
overlying  Lower  Cambric  strata. 

Upon  these  older  coarse  strata  rests  “conformably”  the  Lower  Cambric  series,  the  lithological 
features  of  which  “are  in  strong  contrast”  to  the  older  series  above  described.  The  basal  Cambric 
beds  are  known  as  the  Tapley’s  Hill  slates,  with  a  thickness  of  over  2,000  feet.  These  pass  upward 
into  calcareous  slates  and  finally  into  “a  very  pure  limestone,  oolitic  in  structure,  bluish  in  its 
lower  portions  and  reddish  in  the  upper,”  known  as  the  Brighton  limestone.  It  is  here  that  the 
Lower  Cambric  Archseocyathinae  make  their  appearance.  Still  higher  appear  purple  slates,  then 
quartzites  and  purple  limestones,  together  some  hundreds  of  feet  thick.  It  is  at  the  top  of  this 
series  that  comes  in  the  great  Archaeocyathus  coral  reef  and  other  Cambric  fossils,  now  more  or 
less  transformed  into  marble  beds  fully  200  feet  thick.  The  two  fossiliferous  horizons  are  separ¬ 
ated  from  one  another  by  about  1,000  feet  of  strata.  All  of  the  Cambric  and  lower  strata  are 
now  deformed  into  mountain  ranges. 

Howchin  says  further: 

“The  beds  which  give  evidence  of  glacial  origin  may  be  described  as  consisting  mainly  of 
a  groundmass  of  unstratified,  indurated  mudstone,  more  or  less  gritty,  and  carrying  angular, 
subangular,  and  rounded  boulders  (up  to  11  feet  in  diameter),  which  are  distributed  confusedly 
through  the  mass.  It  is,  in  every  respect,  a  characteristic  till.  The  included  stones  sometimes 
occur  in  pockets  or  groups,  but  the  rock  never  becomes  a  typical  conglomerate.  Coarse  angular 
grits  and  quartzites  often  occur  in  the  form  of  irregular  deposits,  mixed  with  the  finer  ground- 
mass,  and  these  may  or  may  not  carry  boulders.  **  * 

“In  most  sections  there  are  more  or  less  regularly-stratified  beds  or  bands,  which  occur  various 
horizons  in  the  till.  These  may  be  of  quartzite,  finely-laminated  slate,  or  limestone.  The  last- 
named  seldom  exceed  2  or  3  feet  in  thickness,  are  often  gritty,  and  contain  angular  stones. 

“The  occurrence  of  isolated  and  irregularly-distributed  boulders  is  a  constant  feature 
exposures  of  the  gritty  mudstone,  or  till;  but  these  stones  vary  in  size,  relative  numbers,  and  to 
some  extent  in  their  petrological  types,  in  difierent  localities.  A  close-grained  and  very  siliceous 

quartzite  usually  supplies  the  commonest  variety.  ^  .  ,  i  •r+ r 

“Although  the  general  features  of  the  beds  supplied  a  strong  pnma-faae  probability  that 
they  represented  an  ancient  till,  their  glacial  origin  was  not  affirmed  until  the  discovery  of  ice- 


292 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


scratched  boulders  placed  the  question  beyond  doubt.  This  culminating  evidence  was  obtained, 
in  the  first  instance,  at  Petersburg  (on  the  Northern  Railway  from  Adelaide)  in  1901,  and  was  sub¬ 
sequently  confirmed  during  a  visit  to  the  same  place  by  Professor  T.  W.  E.  David,  F.R.S.,  Mr.  E.  F. 
Pittman,  the  Government  Geologist  of  New  South  Wales,  and  myself.  In  association  with  those 
two  experienced  geologists,  fifteen  glaciated  stones  were  obtained  during  a  search  of  two  hours. 

“The  erratics  are  frequently  facetted,  as  well  as  striated,  under  ice-action.  The  strise  vary  in 
depth  and  direction  on  the  same  face,  and  are  often  as  distinct  and  fresh-looking  as  those  which  occur 
on  the  stones  of  the  Pleistocene  Boulder-Clay”  (1908:  239-41).  [The  area  of  tillite  accumulation] 
“was  probably  bounded  on  the  south  and  west  by  moderate  highlands,  consisting  of  pre-Cambrian 
(Algonkian)  quartzites,  schists,  limestones,  and  other  sediments  with  exposed  igneous  batholiths 
and  dikes  of  varied  types.  The  pre-Cambrian  complex  had  been  subjected  to  great  waste  and  was 
probably  in  the  form  of  subdued  relief  at  the  time  of  the  Cambrian  glaciation.  Remnants  of  this 
pre-Cambrian  continent  are  found  in  the  geological  axes  of  the  Mount  Lofty  ranges,  Yorke  Peninsula, 
and  Kangaroo  Island;  the  crystalline  ranges  of  Eyre  Peninsula,  the  porphyrite  outcrops  of  the 
Gawler  ranges,  and  the  igneous  and  metamorphic  plateau  of  Western  Australia. 

“In  no  instance  has  a  glaciated  floor  been  observed,  the  occurrence  of  which  would  suggest 
the  probability  of  ice-action  above  sea-level.  The  absence  of  such  an  ice-marked  floor,  over  the 
area  in  question,  is  not,  however,  to  be  wondered  at  when  in  no  case  have  the  glacial  deposits 
been  discovered  in  contact  with  a  pre-Cambrian  surface.  The  Cambrian  till  is  found  resting 
conformably  on  laminated  quartzites  in  an  orderly  succession,  and  while  the  junction  between 
the  respective  beds  is  always  sharp  and  decided,  it  seems  moderately  certain  that  the  glacial 
debris  was  laid  down  on  a  floor  of  contemporary  marine  deposits — in  which  case  the  agent  of 
distribution  must  have  been  floating  ice.  This  view  is  supported  by  the  fact  that  the  glacial 
material  forms,  practically,  one  continuous  sheet,  spread  over  an  immense  extent  of  country,  and 
maintains  a  remarkable  uniformity  as  to  thickness,  lithological  characteristics,  and  types  of 
erratics  throughout  its  entire  extent.  At  the  same  time  it  is  very  probable  that  the  ice-field  was 
at  no  great  distance  from  this  area  of  deposit”  (1912:  197-8). 

The  following  will  make  it  clear  that  in  all  probability  there  is  a  great  time  hiatus  without 
mountain-making  movements  between  the  Lower  Cambric  and  the  tillite. 

In  the  Onkaparinga  Valley,  about  20  miles  south  of  Adelaide,  a  Lower  Cambric  impure  lime¬ 
stone  rests  sharply  and  without  transition  on  a  series  of  tillite  beds  here  570  feet  thick,  separated 
by  two  thin  quartzite  zones  together  having  a  thickness  of  22  feet. 

In  the  Sturt  Valley  section,  a  few  miles  south  of  Adelaide,  may  also  be  seen  the  contact  between 
the  Lower  Cambric  and  the  tillite.  Here  also  the  basal  Cambric  bed  is  an  impure  dolomitic 
limestone  4  feet  thick,  which  without  transition  rests  “immediately  upon  characteristic  till” 
(1908:  251),  here  nearly  800  feet  thick. 

In  the  Appila-Gorge  section  the  tillite  upper  boundary  “is  marked  by  a  sharp  line  of  division, 
in  which  boulder-clay  with  big  erratics  is  covered  by  a  homogeneous  fissile  slate  or  shale”  (253). 
The  tillite  is  here  about  1,526  feet  thick,  divided  into  three  divisions:  “(a)  An  upper  till  of  120 
feet;  (6)  an  interbedded  series  of  slates  to  656  feet;  and  (c)  a  lower  till  of  750  feet”  (253). 

In  Norway,  according  to  Strahan, 

“The  sandstones  occur  in  the  most  irregular  manner  and  wedge  in  so  suddenly  as  almost  to 
resemble  included  masses;  they  contain  also  fragments  of  shale  more  or  less  rolled,  and  in  this 
and  other  respects  indicate  that  deposition  alternated  with  erosion  under  the  influence  of  variable 
currents.  *  *  *  The  Gaisa  beds  present  only  such  features  as  are  common  to  rocks  of  the 

type  of  the  Wealden,  Trias,  Coal  Measures,  or  Old  Red  Sandstone,  and  give  no  hint  of  the  action 
of  ice.  But  on  visiting  the  section  near  Bigganjargga,  referred  to  by  Dr.  Reusch,  I  found  a  deposit 
of  which  I  have  seen  no  counterpart  in  any  of  those  formations.  *  *  *  ^he  lowest  ledge, 

just  above  high-tide  mark,  a  lenticular  mass  of  darker  rock  [a  tillite]  intercalated  between  the 
ledges  of  sandstone  at  once  arrests  the  attention,  even  as  seen  from  the  deck  of  a  steamer. 

“The  mass  itself  is  a  boulder-rock  quite  unlike  any  of  the  Gaisa  sandstones  or  conglomerates 
which  I  saw  elsewhere.  It  is  referred  to  by  Dr.  Reusch  as  a  conglomerate,  but  from  the  fact  of 
its  being  neither  stratified  nor  waterworn  I  prefer  to  avoid  the  use  of  that  term.  It  may  be 
described  as  a  dark-bluish  or  ashy-grey  friable  rock,  composed  of  a  heterogeneous  mixture  of  grit, 
sand,  and  clay  of  all  degrees  of  coarseness,  and  containing  boulders  ranging  up  to  2  feet  in  length 
scattered  through  it.  Though  quite  unstratified,  it  shows  here  and  there  a  slight  schistose 
structure.  The  included  boulders,  which  are  of  all  shapes  and  lie  at  all  angles,  consist  principally 
of  red  and  grey  granites,  and  of  quartz-grits  resembling  those  of  the  Gaisa  formation.  I  did  not 
succeed  in  finding  any  striated  blocks,  but  the  fact  that  the  matrix  has  been  hardened  and  adheres 


CLIMATES  OF  GEOLOGIC  TIME, 


293 


closely  to  the  boulders  prevented  me  from  examining  more  than  two  or  three  in  the  limited  time 
at  my  disposal.  From  a  similar  boulder-rock  at  Mortensnes,  however,  which  I  unfortunately 
missed  seeing,  Dr.  Reusch  describes  and  figures  well-glaciated  blocks  of  dolomite.  *  *  *  The 

form  of  the  intercalated  mass  of  boulder-rock,  as  well  as  the  fact  that  fragments  of  it  occur  in 
the  base  of  the  overlying  strata,  indicate  that  it  underwent  denudation  before  it  was  buried. 

“The  boulder-rock  rests  on  a  regularly-bedded  sandstone  of  the  usual  type,  and  has  been 
weathered  back  so  as  to  expose  several  square  yards  of  the  remarkably  even  surface  of  that  rock. 
The  platform  thus  exposed  is  not  only  smoothed,  but  conspicuously  and  characteristically  striated. 
The  scratches  can  be  followed  in  some  cases  for  2  or  3  yards,  not  only  up  to  the  foot  of  the  little 
cliff  of  boulder-rock,  but  under  it,  a  fact  of  which  I  made  certain  by  wedging  out  some  masses  of 
that  material  and  exposing  a  fresh  portion  of  the  platform.  *  *  *  The  sandstone  is  traversed 

by  a  few  irregular  joints,  the  lines  due  to  which,  however,  on  the  striated  platform  bear  no  resem¬ 
blance  to  glacial  groovings.  The  striae  have,  beyond  question,  been  cut  into  that  surface  indepen¬ 
dently  of  any  structure  possessed  by  the  rock,  and  are  in  all  respects  characteristic  glacial  markings. 

“The  evidence  detailed  above  seems  to  leave  no  room  for  doubt  that  we  have  here  an  inter¬ 
calation  of  a  true  glacial  till  in  the  Gaisa  formation.  *  *  *  j  accept  without  hesitation  Dr. 

Reusch’s  conclusion  that  the  phenomena  are  due  to  glacial  action,  and  that  they  were  produced 
contemporaneously  in  the  Gaisa  formation”  (1897:  140-43). 

“The  Gaisa  beds,  so  far  as  I  saw  them,  do  not  suggest  the  immediate  neighbourhood  of  a 
mountain-region,  for  such  conglomerates  as  they  contain  are  neither  coarse  nor  plentiful.  The 
facts  tend  rather  to  indicate  a  temporary  deterioration  of  climate”  (145). 


UNDATED  PROTEROZOIC  GLACIATION  OF  CHINA. 

Nan-t’ou  formation. — A  series  of  sandy  and  argillaceous  rocks  seen  only  beneath  the  Cambric 
limestone  cliffs  at  Nan-t’ou  (long.  110°  E.,  lat.  31°  N.).  The  basal  strata,  Blackwelder  states, 
“consist  of  arkose  sandstone  and  conglomerate,  which  are  purplish-brown  in  color  below,  but 
gradually  become  white  and  purely  quartzose  in  the  upper  strata.  Throughout  the  total  thickness 
of  perhaps  150  feet,  45  meters,  the  texture  is  coarse  and  gritty”  (1907:  267). 

He  says  further: 

“The  upper  member  of  the  formation  is  distinct  from  the  sandstone,  but  we  did  not  see  the 
contact  and  do  not  know  the  exact  relations. 

“The  next  outcrops  above  the  sandstone  occur  100  feet,  30  rneters,  up  the  slope,  and  expose 
about  120  feet,  35  meters,  of  hard  massive  boulder-clay  or  tillite,  which  is  neither  fissile  nor 
stratified.  It  is  a  greenish  gritty  clay-rock  of  hackly  fracture,  in  which  lie  irregular  stones  of 

various  sizes  and  kinds,  with  their  long  axes  at  random  angles  with  the  horizontal.  *  *  *  'pj^g 

rocks  range  in  size  from  sand-grains  to  blocks  50  to  75  cm.  in  length,  and  there  is  no  suggestion 
of  the  assortment  of  the  individual  sizes.  Coarse  and  fine  particles  lie  indiscriminately  mingled 
and  chaotic  in  their  arrangement.  The  forms  of  the  majority  of  the  stones  are  subangular,  e., 
angles  are  present,  but  are  smooth  and  rounded.  The  flattish  surfaces  of  such  slowly  weathering 
rocks  as  the  massive  siliceous  ferruginous  limestone  are  polished  and  scratched  in  various  direc¬ 
tions,  and  are  identical  in  aspect  with  pebbles  from  the  Pleistocene  boulder-clays  of  Aorth  America 
and  Europe.  The  scratched  stones  were  found  in  numbers  firmly  fixed  in  the  green  tillite,_  in 
such  a  condition  as  to  show  that  they  had  never  been  disturbed  nor  subjected  to  surface  abrasion 
since  they  were  imbedded  there  in  early  Paleozoic  time.  j  f  •+ 

“The  promiscuous  arrangement  of  the  pebbles,  the  heterogeneity  of  the  mass  aud  oi  its 
lithologic  components,  the  subangular  shapes  of  the  stones  and  espepially  their  striated  surfaces 
are  positive  characteristics  of  glacial  till.  The  evidence  of  glacial  origin  is  P  ^ 

usually  seen  in  the  Pleistocene  of  the  United  States  or  Gr^t  Britain.  is  ng  y 

probable  that  these  glacial  beds  on  the  Yang-tzi  are  of  early  Cambrian  age  (  )• 

To  this  Willis  adds:  ^  i  j  oio 

“Nan-t’ou  tillite.— The  Nan-t’ou  glacial  deposit  occurs  in  longitude  111  east,  latitude  31 
north,  about  200  feet,  60  meters,  above  sea.  It  evidently  accumulated  close  to  J^a-level  m 
early  Sinian  [=  Cambric]  time,  as  it  is  overlain  by  marine  hmestones  of  ^ 

the  plane  of  the  pre-Sinian  unconformity  is  characteristically  f Azite  is 
bedded  quartzite,  which  may  have  been  either  river  deposit  or  f 

generally  covered  in  the  type  locality  and  a  cultivated  slope  in  errup  about  as  hard  as 

30  meters.  Above  the  terraced  fields  occur  steep  banks  of 
unweathered  shale,  of  irregular  hackly  fracture,  not  stratified, 

of  various  kinds  aid  sizes,  many  of  which  are  striated.  The  thickness  seen  is  120  feet,  30  meters. 


294 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


“At  the  top  of  the  tillite,  beneath  a  cliff,  is  a  well-exposed  contact  with  the  overlying  lime¬ 
stone.  The  tillite  passes  into  a  greenish  shale,  consisting  of  the  same  materials,  including  char¬ 
acteristic  pebbles,  all  rearranged  by  the  water.  This  shale  conglomerate  is  about  2  feet  thick  and 
grades  into  the  overlying  limestone,  the  basal  layer  of  a  great  thickness  of  Sinian. 

“The  facts  clearly  demonstrate  the  presence  at  this  spot  of  a  glacier  which  gave  way  to  marine 
waters  and  left  a  deposit  of  till  that  was  slightly  washed  by  waves  before  it  was  buried  beneath 
calcareous  mud.  *  *  * 

“Whether  the  Nan-t’ou  glacier  was  an  exceptional  occurrence  or  a  representative  of  an  ex¬ 
tensive  system,  only  in  degree  affects  the  deduction  that  the  temperature  of  early  Sinian  time  was 
low.  Glaciation  in  latitude  31°  near  sea-level  presents,  it  is  true,  a  problem  which  refrigeration 
alone  will  not  solve,  especially  as  no  traces  of  contemporaneous  glaciers  have  been  found  farther  north ; 
but  there  can  be  no  doubt  that  it  signifies  severe  cold  throughout  northern  Asia”  (1909:  39-40). 

Professor  J.  P.  Iddings,  while  on  a  geologic  tour  in  China,  visited  the  Nan-t’ou  region  in  October 
1909,  and  from  him  has  been  received  the  following  description  of  the  tillites: 

“The  tillite  is  extensive  and  quite  persistent  in  character,  though  somewhat  variable  in  thick¬ 
ness.  It  is  interbedded  with  the  basal  sandstone  resting  on  the  granite-gneiss,  and  I  did  not  find 
it  in  contact  with  the  granite.  I  first  examined  the  locality  discovered  by  Willis  and  Blackwelder. 
*  *  *  The  formation  extends  for  3  or  4  miles  back  from  the  Yangtsze  to  the  north  along 

the  base  of  the  cliff  of  limestone.  Some  distance  back  from  the  river,  I  crossed  the  branch  creek 
that  enters  the  Yangtsze  at  Nantou.  The  branch  is  in  granite  which  rises  in  the  east  slope  about 
400  feet.  Here  occurs  the  base  of  the  conglomeratic  red  sandstone,  dipping  5°  SE.,  strike  N.  40° 
E.  (magnetic).  The  top  of  the  sandstone  is  200  feet  higher.  The  upper  50  feet  contain  white 
layers,  alternating  with  red.  Near  the  base  of  the  tillite  there  are  some  thin  clay  layers  in  the 
sandstone,  and  in  the  base  of  the  tillite  is  some  red  sandy  rock.  The  two  appear  to  mix  and  to 
grade  into  one  another.  Similar  mixture  and  gradation  were  observed  in  numerous  places  farther 
north.  The  tillite  at  the  location  on  the  branch  creek  is  green  and  of  the  same  aspect  as  in  other 
places  visited.  It  contains  many  boulders  and  pebbles  in  the  middle  portion;  not  so  many  in  the 
basal  or  in  the  uppermost  portions.  There  were  no  signs  of  bedding,  and  no  intercalated  stratum 
of  sandstone,  as  in  a  case  south  of  Huang-Ling-Miao  noted  later.  The  tillite  is  about  150  feet  thick 
and  is  overlain  by  limestone,  the  bottom  layer  of  which  is  more  massive  than  the  higher  layers. 

“  Traveling  northward  across  spurs  that  set  forth  from  the  cliffs  east  of  a  branch  stream,  the 
base  of  the  sedimentary  rocks  rises  gradually  as  far  as  I  went,  about  3.5  miles  in  a  direct  line 
from  Yangtsze  Kiver.  I  observed  a  fault  cutting  across  the  spurs  shifting  the  exposures  of 
tillite,  the  trend  of  the  fault  being  about  with  the  strike  (about  N.  45°  E.),  and  the  hade  very 
steep,  about  75°,  apparently  to  the  west,  though  not  distinct.  The  strata  and  the  granite  on  the 
west  were  raised  with  respect  to  the  same  on  the  east,  the  displacement  being  about  100  feet. 
The  result  is  apparent  variableness  in  the  thickness  of  the  tillite  bed,  and  to  cause  it  in  places  to 
a^ut  against  the  granite. 

“  Crossing  to  south  side  of  Yangtsze  opposite  Nantou,  I  followed  the  base  of  the  stratified  rocks 
westward  as  they  rose  above  the  granite,  and  occasionally  saw  exposures  of  tillite.  Back  of 
Huang-Ling-Miao,  granite  extends  up  spurs  to  1,700  feet  above  the  river;  then  follow  about  300 
feet  of  massive  strata  of  red  sandstone,  which  is  immediately  overlain  by  tillite,  the  lower  5 
feet  of  tillite  having  a  layer  of  sandstone  blended  with  it.  There  are  few  boulders  in  the  lowest 
part,  but  more  higher  up.  The  pebbles  are  of  granite,  gneiss,  porphyry,  slate,  limestone,  flint, 
and  quartz.  The  lower  portion  of  tillite  is  yellow  and  clayey,  the  upper  portion  is  green  and 
indurated,  as  at  Tungling.  About  200  feet  from  the  base  is  a  massive  stratum  of  red  sandstone, 
about  6  feet  thick,  having  the  same  strike  and  dip  as  the  strata  above  and  below  it.  Above  this 
there  is  tillite  for  200  feet  more,  making  the  thickness  of  the  tillite  in  this  locality  between  400  and 
500  feet.  The  overlying  limestone  is  somewhat  brecciated  at  its  base  for  6  inches  to  a  foot,  and 
then  becomes  massive,  with  some  contortions  of  the  lines  of  bedding,  for  a  thickness  of  3  or  4 
feet.  Then  follows  thinly  bedded  to  fissile  arenaceous  limestone,  and  layers  of  arenaceous  shales 
quite  uniform  in  character  up  to  about  2,700  feet  above  the  river.  The  strike  of  the  strata  is 
N.  45°  E.,  dip  10°  SE.  No  trace  of  fossils  was  seen,  though  there  were  fine  exposures  of  strata 
and  talus.  The  cliffs  rise  to  about  3,500  feet  above  the  river.  The  area  of  granite  hills  north  of 
Yangtsze  River  was  well  seen  from  a  high  spur  south  of  the  river.  The  sedimentary  strata  were 
seen  to  arch  in  a  dome  around  flanks  of  the  granite  hills  to  west  and  north  and  to  east  and  north. 
South  of  the  river  sedimentary  strata  appear  to  extend  in  an  arch  around  to  Tungling,  at  the 
lower  entrance  to  Lukan  gorge  on  the  west  side  of  the  granite  arch. 

“At  Tungling  the  tillite  is  seen  on  both  sides  of  Yangtsze  River,  near  the  shores.  On  the  north 
side,  in  a  bluff  near  the  landing,  it  is  about  300  feet  thick.  The  tillite  here  overlies  red  basal 


CLIMATES  OF  GEOLOGIC  TIME. 


295 


sandstone,  bi^  the  contact  is  not  exposed.  The  tillite  is  overlain  by  a  massive  stratum  of  lime- 
stone  and  of  fissile  layers,  and  then  by  thicker  strata  of  limestone.  No  fossils  were  found  in  the 
limestone  or  m  the  talus  at  the  base  of  the  cliffs  to  the  west  of  Tungling. 

‘'On  the  south  side  of  the  river,  opposite  Tungling,  tillite  is  well  exposed  on  the  beach  near 
the  water  beneath  limestone,  with  strike  N.  and  S.,  and  a  dip  25°  W.  The  tillite  is  well  indurated, 
and  carries  fewer  boulders  in  its  upper  than  in  its  lower  portion.  The  erratics  embrace  granite, 
gneiss,  quartz-porphyry,  slate,  limestone,  and  quartz.  The  tillite  is  here  about  250  feet  thick, 
and  rests  on  red  sandstone,  the  contact  with  which  is  seen  for  a  short  distance  only.  The  under- 
lying  sandstone,  about  100  feet  thick,  becomes  more  pebbly  and  conglomeratic  toward  its  base, 
and  is  arkose  near  its  bottom.  It  rests  on  decomposed  hornblende-schist,  no  granite  being  seen 
here  on  the  south  side  of  the  river.  On  the  north  side  there  is  decomposed  granite  beneath  the 
sandstone,  and  farther  off  there  is  hornblende-schist. 

“From  these  observations  it  appears  as  though  the  tillite  extended  continuously  from  where  it 
is  seen  beneath  the  limestone  east  of  Nantou,  around  the  south  flank  of  the  granite-gneiss  area, 
to  and  beneath  the  limestone  cliff  west  of  Tungling,  and  that  it  extends  northward  from  Nantou 
at  least  some  distance.  It  appears  to  be  thickest  south  of  Huang-Ling-Miao  and  thinnest  in 
its  extension  toward  the  northeast. 

“I  spent  parts  of  five  days  in  five  different  places  hunting  for  fossils  without  seeing  one,  so 
they  must  be  scarce.  The  rocks  appear  to  be  free  from  trace  of  them  for  some  hundreds  of  feet 
in  thickness,  as  I  examined  carefully  the  talus  below  several  high  cliffs.  I  was  disappointed  not 
to  find  any.” 

From  the  fact  that  no  one  has  yet  found  fossils  in  the  very  thick  and  well-exposed  dolomites 
that  overlie  the  tillites  in  the  immediate  area  of  the  glacial  deposits,  the  question  may  well  be 
asked:  How  do  we  know  that  the  dolomites  at  their  base  are  of  Middle  Cambric  age?  In  order 
to  answer  this  question,  the  writer  corresponded  with  Blackwelder  on  the  subject,  receiving  the 
following  reply  under  date  of  March  24,  1913. 

“In  the  Yangtze  region  there  are  two  very  thick  massive  limestone  formations,  neither  of  them 
rich  in  fossils,  but  both  with  their  own  distinctive  lithologic  characters.  These  are  separated  by  an 
easily  recognized  body  of  green  shale.  In  crossing  the  mountains  north  of  the  Yangtze  River,  and 
in  following  down  the  great  gorges  of  the  latter,  these  formations  were  repeated  again  and  again  in 
great  open  anticlines  and  synclines,  interrupted  by  only  occasional  faults.  The  age  of  the  lower 
massive  limestone  was  approximately  fixed  by  the  finding  of  a  rich  Mohawkian  fauna  near  the  top 
of  it,  perhaps  50  miles  north  of  the  Yangtze  River. 

“The  Middle  Cambrian  fossils  which  were  found  several  days’  journey  northwest  of  the  tillite 
exposure,  came  from  rocks  very  highly  folded  and  faulted,  so  that  their  stratigraphic  relations  are 
uncertain.  Lithologically,  however,  the  beds  were  much  like  those  just  below  the  great  cliff  lime¬ 
stone  at  Nan-t’ou,  in  that  they  contained  many  layers  of  gray  and  black  oolite.  I  think  it  highly 
probable  that  the  horizon  of  the  Middle  Cambrian  fossils  is  not  more  than  a  few  hundred  feet  above 
the  tillite  and  is  beneath  the  great  chff  limestone.” 

On  the  ground  that  none  of  the  Lower  Cambric  faunas  indicate  cool  or  cold  waters  and  in 
view  of  the  further  fact  that  in  many  widely  separated  places  there  are  reef-making  corals 
(Archaeocyathinae) ,  the  writer  does  not  regard  the  Yangtze  tillites  as  of  Cambric  age.  He  would, 
rather,  refer  them  to  the  Proterozoic,  but  whether  they  are  late  or  early  in  this  era  remains  to  be 
determined  on  the  basis  of  the  age  of  the  superposed  dolomites. 

EARLIEST  PROTEROZOIC  GLACIATION  OF  CANADA. 

Coleman  says: 

“For  several  years  it  has  seemed  to  me  very  probable  that  there  was  a  still  more  ancient 
ice  age,  at  the  beginning  of  the  Lower  Huronian  in  the  Archean  as  defined  in  Canada,  or  the 
Archeozoic  or  lowest  Algonkian,  as  defined  by  various  American  geologists.  The  so-called 
Huronian  ‘slate  conglomerate’  of  Ontario  has  attracted  attention  ever  since  Logan  and  Mmray 
mapped  and  described  it  in  the  typical  region  north  of  Lake  Huron,  nearly  fifty  years  ago.  Good 
descriptions  of  it  are  given  by  Logan  in  the  1863  report  of  the  Canadian  Geological  ourvey, 
where  he  refers  to  the  different  kinds  of  rock  enclosed  as  pebbles  or  bowlders,  granite,  lelsite, 
certain  greenstones  and  jasper,  for  example;  and  describes  the  matrix  as  sometimes  slaty,  some¬ 
times  more  quartzitic  or  like  diorite  or  greenstone.  At  present  the  matrix  would  generally  be 
called  graywacke  or  slate,  though  sometimes  it  is  schistose  or  looks  like  an  eruptive  rock. 


296 


THE  CLIMATIC  FACTOR  AS  ILLUSTRATED  IN  ARID  AMERICA. 


“The  pebbles  or  bowlders  are  in  many  cases  subangular  or  sharply  angular  and  are  found 
miles  away  from  any  known  source;  and  as  they  may  be  of  any  size  up  to  blocks  weighing  tons, 
and  are  frequently  very  sparsely  scattered  through  an  unstratified  matrix,  a  stone  or  two  in 
several  yards,  one  can  not  help  suspecting  that  the  transporting  agency  was  ice  rather  than  water. 
There  are  parts  of  the  formation  where  the  pebbles  or  stones  are  well  rounded  and  crowded  in 
certain  bands.  In  such  cases  they  are  probably  true  water-formed  conglomerates;  but  the 
prevalent  type  of  the  rock  with  scattered  subangular  stones  or  bowlders  should  not  be  called  a 
conglomerate,  any  more  than  a  Pleistocene  bowlder  clay  would  receive  that  name.  The  appear¬ 
ance  of  these  so-called  slate  or  graywacke  conglomerates  is  closely  like  that  of  the  Dwyka  bowlder 
clays,  for  which  Penck  suggests  the  term  ‘tillite’;  *  *  *  rocks  of  the  kind  are  found  from 

point  to  point  across  all  northern  Ontario,  a  distance  of  nearly  800  miles,  and  from  the  north  shore 
of  Lake  Huron  in  latitude  46°  to  Lake  Nipigon  in  latitude  50°. 

“The  more  schistose  of  these  conglomerates  have  their  pebbles  flattened  and  rolled  out  into 
lenses  not  at  all  suggesting  glacial  action;  but  the  fact  that  all  of  them,  whether  schistose  or  un¬ 
modified,  occupy,  so  far  as  known,  the  same  position,  immediately  over  the  Keewatin,  and  con¬ 
tain  pebbles  and  bowlders  of  the  same  rocks,  granite,  banded  jasper,  etc.,  makes  it  very  probable 
that  they  belong  to  the  same  age  and  have  had  a  similar  origin.  *  *  * 

“By  the  exercise  of  care  and  patience  it  has  been  possible  to  break  from  their  matrix  wholly 
or  partially  about  twenty  of  these  stones,  mostly  only  an  inch  or  two  in  diameter,  but  half  a 
dozen  from  3  to  6  inches  across.  As  coarse-grained  rocks  like  granite  seldom  show  distinct 
striations  in  modern  bowlder  clays,  felsites  and  fine-grained  greenstones  were  selected  to  work 
upon.  Of  the  twenty  stones  four  or  five  are  more  or  less  striated,  but  only  one  is  heavily  and 
decisively  scored.  Unfortunately  the  matrix  could  not  be  completely  removed  from  this  one, 
but  the  exposed  surfaces  show  the  striations  well  on  one  face  and  distinctly  on  two  others. 

“Several  of  the  smaller  pebbles  have  the  peculiar  somewhat  uneven  but  well-polished  faces 
with  rougher  corners  so  often  seen  in  the  smaller  stones  of  bowlder  clay. 

“Though  the  number  of  stones  available  is  small,  the  proportion  showing  more  or  less  stri- 
ation  is  as  large  as  in  recent  bowlder  clay  and  all  the  usual  features  of  ice-carved  stones  are  found 
in  them.  It  may  be  added  that  they  were  taken  from  undisturbed  parts  of  the  formation  with 
no  faulting  to  cause  slickensides,  and  that  the  stones  themselves  had  not  been  squeezed  nor  broken 
in  the  matrix. 

“No  striated  surfaces  were  found  where  the  conglomerate  rested  on  the  underlying  Keewatin; 
but  the  only  contact  of  the  two  rocks  examined  was  unfavorable  for  displaying  such  a  surface. 
[Such  are  now  known  in  three  places  and  were  described  in  1912.]  Mining  operations  show  that 
the  rocks  beneath  the  Huronian  have  on  the  whole  an  uneven,  somewhat  undulating  surface  of 
low  hills  and  valleys,  the  conglomerate  often  more  or  less  filling  in  these  valleys.  *  *  * 

“The  evidence  for  a  Lower  Huronian  Ice  Age  may  be  summed  up  as  follows: 

“A  peculiar  rock  consisting  of  graywacke  or  finer  materials  showing  little  or  no  stratification 
but  containing  pebbles  or  stones,  sometimes  crowded,  but  more  often  scattered  a  few  feet  apart, 
is  found  from  point  to  point  over  an  area  800  miles  long  by  250  miles  broad.  The  stones  are  of 
all  sizes  up  to  diameters  of  several  feet  and  of  all  shapes  from  rounded  to  angular,  many  being 
subangular  with  rounded  corners.  The  stones  are  of  several  different  kinds,  some  fragments  of 
the  immediately  underlying  rock,  others  having  a  distant  source. 

“In  the  Cobalt  mining  region  a  few  polished  and  striated  stones  have  been  broken  out  of  the 
matrix.  They  are  closely  like  stones  from  the  Pleistocene  bowlder  clay  of  the  same  region  except 
that  they  lack  the  Niagara  limestones  of  the  recent  drift. 

“  Hand  specimens  of  matrix  and  enclosed  pebbles  are  precisely  like  the  Dwyka  tillite  or  con¬ 
glomerate  of  South  Africa,  which  is  undoubtedly  of  glacial  origin. 

“  Against  the  glacial  theory  is  the  fact  that  no  roches  moutonnees  have  yet  been  found  on  the 
underlying  Keewatin  rocks.  All  the  positive  evidence  is  favorable  to  the  theory  of  glacial  action 
as  the  cause  of  these  curious  bowlder-strewn  rocks. 

“  If  the  evidence  given  above  is  accepted,  the  occurrence  of  glaciation  is  probable  over  an  area 
too  large  to  be  the  work  of  merely  local  mountain  glaciers,  and  one  must  assume  the  presence  of 
ice-sheets  comparable  to  those  which  formed  the  Dwyka. 

“  The  Lower  Huronian  is  the  second  formation  in  the  geological  succession  in  North  America, 
only  the  Keewatin  coming  before  it;  so  that  the  probable  action  of  ice  on  a  large  scale  is  pushed 
back  almost  to  the  beginning  of  known  geological  time.  This  implies  that  the  climates  of  the 
earlier  parts  of  the  world’s  history  were  no  warmer  than  those  of  later  times,  and  that  in  Lower 
Huronian  times  the  earth’s  interior  heat  was  not  sufficient  to  prevent  the  formation  of  a  great 
ice-sheet  in  latitude  46° ”  (1907:  188-92). 


BIBLIOGRAPHY, 


PERMIC  GLACIATION. 

Chamberlin,  T.  C.,  and  Salisbury,  II.  D.,  1906.  Geology.  II:  632-639,  655-677. 

Coleman,  A.  P.,  1908.  Glacial  periods  and  their  bearing  on  geological  theories.  Bull.  Geol.  Soc.  America,  19:  347- 
366. 

David,  T.  W.  E.,  1896.  Evidences  of  glacial  action  in  Australia  in  Permo-Carboniferous  time.  Quart.  Jour.  Gcol. 
Soc.  London,  52:  289-301. 

- ,  1907.  Conditions  of  climate  at  different  geological  epochs,  with  special  reference  to  glacial  epochs.  Compte 

Rendu,  Congres  G6ol.  Internat.,  Mexico:  449-482. 

Hatch,  F.  H.,  and  Corstorphine,  G.  S.,  1909.  The  geology  of  South  Africa.  2d  cd.:  219-243,  335-339. 

Kayser,  E.,  1911.  Lehrbuch  der  Geologic.  4th  ed.,  II:  263-318. 

Koken,  E.,  1907.  Indisches  Perm  und  die  permische  Eiszeit.  N.  Jahrb.  fiir  Min.,  Geol.,  etc.,  Festband:  446-546. 

Ramsay,  A.  C.,  1855.  On  the  occurrence  of  angular,  subangular,  polished,  and  striated  fragments  and  boulders  in 
the  Permian  breccia  of  Shropshire,  etc.  Quart.  Jour.  Geol.  Soc.  London,  11:  185-205. 

Sayles,  R.  W.,  and  La  Forge,  L.,  1910.  The  glacial  origin  of  the  Roxbury  conglomerate.  Science,  n.s.,  32 :  723-724. 

Schwarz,  E.  H.  L.,  1906.  The  three  Palseozoic  ice-ages  of  South  Africa.  Jour.  Geol.,  14:  683-691. 

White,  I.  C.,  1908.  Final  report  of  the  chief  of  the  Brazilian  Coal  Commission  (Commissao  de  Estudos  das  Minas 
de  Carvao  de  Pedra  do  Brazil):  11-14,  29-55,  227-233. 

Woodworth,  J.  B.,  1912a.  Boulder  beds  of  the  Caney  shales  at  Talihina,  Oklahoma.  Bull.  Geol.  Soc.  America, 
23:  457-462. 

- ,  1912b.  Geological  expedition  to  Brazil  and  Chile,  1908-1909.  Bull.  Mus.  Comp.  Zook,  56:  79-82. 


DEVONIC  GLACIATION. 

Geikie,  a.,  1903.  Text  book  of  geology.  4th  ed.,  II:  1001,  1011. 

Hatch,  F.  H.,  and  Corstorphine,  G.  S.,  1909.  The  geology  of  South  Africa.  2d  ed. :  62-78. 

Rogers,  A.  W.,  1905.  An  introduction  to  the  geology  of  Cape  Colony:  94-121. 

Rogers,  A.  W.,  and  Schwarz,  E.  H.  L.,  1901.  Report  on  the  geology  of  the  Cederbergen  and  adjoining  country. 

Ann.  Rept.  Geol.  Comm.  Cape  Colony,  1898:  65-82. 

Schwarz,  E.  H.  L.,  1906.  The  three  Palseozoic  ice-ages  of  South  Africa.  Jour.  Geol.,  14:  683-691. 


PROTEROZOIC  GLACIATION. 


Coleman,  A.  P.,  1907.  A  Lower  Huronian  ice-age.  Amer.  Jour.  Sci.  (4),  23:  187-192. 

- ,  1908a.  Glacial  periods  and  their  bearing  on  geological  theories.  Bull.  Geol.  Soc.  America,  19:  347-366. 

- ,  1908b.  The  Lower  Huronian  ice-age.  Jour.  Geol.,  16:  149-158. 

- ,  1912.  The  Lower  Huronian  ice-age.  Compte  Rendu,  CongrSs  G6ol.  Internat.,  Stockholm:  1069-1072. 

David,  T.  W.  E.,  1907.  Glaciation  in  Lower  Cambrian,  possibly  in  pre-Cambrian  time.  Compte  Rendu,  Congres 
G6ol.  Internat.,  Mexico:  271-274;  Conditions  of  climate  at  different  geological  epochs,  with  special 
reference  to  glacial  epochs,  Ihid. :  440-446. 

Geikie,  A.,  1880.  A  fragment  of  primeval  Europe.  Nature,  22  :  400-403. 

- ,  1903.  Text  book  of  geology.  4th  ed.,  II:  891,  899,  1309. 

Howchin,  W.,  1908.  Glacial  beds  of  Cambrian  age  in  South  Australia.  Quart.  J  our.  Geol.  Soc.  London,  54 :  234-259. 
- ,1912.  Australian  glaciations.  Jour.  Geol.,  20:  193-227. 

Miller,  W.  G.,  1911.  A  geological  trip  in  Scotland.  Canadian  Mining  Jour.,  Feb.  15  and  March  1. 

Peach,  B.  N.,  1912.  The  relation  between  the  Cambrian  faunas  of  Scotland  and  North  America.  Nature,  90:  49-o6. 
Reusch,  H.,  1891.  Det  nordlige  Norges  geologi.  Norges  geol.  Undersogelse:  26-34. 

Schwarz,  E.  H.  L.,  1906.  The  three  Palseozoic  ice-ages  of  South  Africa.  Jour.  Geol.,  14:  683-691.  ^ 

Strahan,  a.,  1897.  On  glacial  phenomena  of  Palieozoic  age  in  the  Varanger  Fiord.  Quart.  Jour.  Geol.  Soc.  London, 

53:  137-146. 


Vredenburg,  E.  W.,  1907.  A  summary  of  the  geology  of  India:  19  23.  l  at  t  t)*  t. 

Willis,  B.,  and  Blackwelder,  E.,  1907,  1909.  Research  in  China.  Cam.  Inst.  I\ash.  Pub.  hio.  54,  I,  Pt.  I:  -64 

269;  II:  39-40. 


297 


298 


BIBLIOGRAPHY. 


GENERAL. 

Adams,  F.  D.,  and  Barlow,  A.  E.,  1910.  Geology  of  the  Haliburton  and  Bancroft  areas  (Ontario).  Geol.  Surv. 
Canada,  Mem.  6. 

Barrell,  J.,  1907.  Origin  and  significance  of  the  Mauch  Chunk  shale.  Bull.  Geol.  Soc.  America,  18;  449-476. 

- ,  1908.  Relations  between  climate  and  terrestrial  deposits.  Jour.  Geol.,  16:  159-190,  255-295,  363-384. 

- ,  1912.  Criteria  for  the  recognition  of  ancient  delta  deposits.  Bull.  Geol.  Soc.  America,  23:  377-446. 

Bastin,  E.  S.,  1910.  Origin  of  certain  Adirondack  graphite-deposits.  Econ.  Geol.,  5:  134-157. 

Berry,  E.  W.,  1910.  An  Eocene  flora  in  Georgia  and  the  indicated  physical  conditions.  Bot.  Gazette,  50:  202-208. 

- ,  1912.  Contributions  to  the  Mesozoic  flora  of  the  Atlantic  coastal  plain.  VIII.  Texas.  Bull.  Torrey  Bot. 

Club,  39:  387-406. 

Clarke,  F.  W.,  1911.  The  data  of  geochemistry.  Bull.  491,  U.  S.  Geol.  Surv. 

Dall,  W.  H.,  1895.  Contributions  to  the  Tertiary  fauna  of  Florida.  Trans.  Wagner  Free  Inst.  Science,  III,  Pt.  6: 
1547-1551. 

- ,  1904.  The  relations  of  the  Miocene  of  Maryland  to  that  of  other  regions  and  to  the  recent  fauna.  Maryland 

Geol.  Surv.,  Miocene  volume:  cxxxrx-CLV. 

- ,  1907.  On  climatic  conditions  at  Nome,  Alaska,  during  the  Pliocene.  Amer.  Jour.  Sci.,  (4),  23:  457-458. 

Dep^ret,  C.,  1909.  The  transformations  of  the  animal  world. 

Gorget,  R.,  1911.  Die  Entwickelung  der  Lehre  von  den  Salzlagerstatten.  Geol.  Rundschau,  2:  278-302. 
Handlirsch,  A.,  1908.  Die  fossilen  Insekten. 

- ,  1910a.  Das  erste  fossile  Insekt  aus  dem  Oberkarbon  Westfalens.  Verb.  d.  k.  k.  zool.-bot.  Gesell.  Wien, 

60;  177-183. 

- ,  1910b.  Die  Bedeutung  der  fossilen  Insekten  fiir  die  Geologic.  Mitt.  Geol.  Gesell.  Wien,  3  :  503-522. 

Kayser,  E.,  1911.  Lehrbuch  der  Geologic.  4th  ed.,  II:  471-472. 

Knowlton,  F.  H.,  1910a.  In  Willis  and  Salisbury,  Outlines  of  geologic  history,  chapter  10. 

- ,  1910b.  The  Jurassic  age  of  the  “Jurassic  flora  of  Oregon.”  Amer.  Jour.  Sci.  (4),  30:  33-64. 

- ,  1910c.  Biologic  principles  of  paleogeography.  Pop.  Sci.  Monthly,  76:  601-603. 

Koken,  E.,  1893.  Die  Vorwelt  imd  ihre  Entwickelungsgeschichte. 

Lawson,  A.  C.,  and  Walcott,  C.  D.,  1912.  The  geology  of  Steeprock  Lake,  Ontario;  Notes  on  the  fossils  from  lime¬ 
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Nathorst,  a.  G.,  1912.  On  the  value  of  the  fossil  floras  of  the  Arctic  regions  as  evidence  of  geological  climates. 
Ann.  Rep.  Smithsonian  Inst,  for  1911:  335-344. 

Neumatr,  M.,  1883.  Ueber  klimatische  Zonen  wahrend  der  Jura-  und  ICreidezeit.  Denk.  d.  k.  Akad.  d.  Wiss., 
Math.-Nat.  Classe,  Wien,  47:  277-310. 

Osborn,  H.  F.,  1910.  The  age  of  mammals  in  Europe,  Asia,  and  North  America. 

PoMPECKJ,  J.  F.,  1910.  Zur  Rassenpersistenz  der  Ammoniten.  Geol.  Abth.  d.  Naturh.  Gesell.  zu  Hannover:  63-83. 
Ramsay,  W.,  1910.  Orogenesis  und  Klima.  Oversigt  af  Finska  Vet.-Soc.  Forhandl.,  52:  1-48. 

Roemer,  F.,  1852.  Die  Kreidebildungen  von  Texas. 

ScHCCHERT,  C.,  1910.  Paleogeography  of  North  America.  Bull.  Geol.  Soc.  America,  20  :  427-606. 

Smith,  J.  P.,  1912a.  Ancient  portals  of  the  earth.  Pop.  Sci.  Monthly,  79:  393-399. 

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Staff,  H.  von,  and  Wedekind,  R.,  1910.  Der  Oberkarbone  Foraminiferen-Sapropelit  Spitzbergens.  Bull.  Geol. 
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Stanton,  T.  W.,  1910.  Paleontologic  evidences  of  climate.  Pop.  Sci.  Monthly,  77:  67-70. 

Stromer,  E.,  1909.  Lehrbuch  der  Palaeozoologie. 

Vaughan,  T.  W.,  1910.  A  contribution  to  the  geologic  history  of  the  Floridian  plateau.  Cam.  Inst.  Wash.  Pub. 
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238-252. 

Walcott,  C.  D.,  1910.  Abrupt  appearance  of  the  Cambrian  fauna  on  the  North  American  continent.  Smithsonian 
Misc.  Coll.,  57:  1-16. 

Walther,  j.,  1908.  Geschichte  der  Erde  und  des  Lebens. 

White,  D.,  1907.  Permo-Carboniferous  climatic  changes  in  South  America.  Jour.  Geol.,  15:  615-633. 

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PART  III. 


STATISTICS. 


Table  A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

I. 

J. 


Av6rage  Growth  of  451  Soquoia  Trees  in  California  by  decades  and  centuries 
of  the  life  of  the  trees,  beginning  with  their  youth.  See  figures  35  and  36. 

Comparative  Growth  of  Short-lived  and  Long-lived  Sequoias  by  Groups. 
Corrective  Factor  for  Longevity.  See  figure  37. 

List  of  Individual  Sequoia  Trees  measured  in  California  in  1911  and  1912. 
Summary  of  Sequoia  Trees  by  Groups. 

Combined  Corrective  Factors  for  Age  and  for  Longevity,  Sequoia  washing- 
toniana.  See  figures  35  and  36. 

Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade. 

Summary  of  Growth  of  Sequoia  washingtoniana.  Trees  measured  in  1911 
and  1912.  By  groups  corrected  and  uncorrected,  including  Caspian  Factor. 
See  figures  38,  50,  and  72. 

Summary  of  Growth  of  Trees  measured  by  the  United  States  Forest  Service. 
See  figure  31. 

Average  Annual  Growth  of  Sequoias.  See  figures  42,  43,  44,  and  48. 

Errors  of  Ring  Counting  in  Northern  Arizona  Pines.  (Compiled  by  A.  E. 
Douglass.) 


299 


V 


,  •  «-.  rr  o. 


f-  ; 


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. 


yir^ 


*  -  M 


.JT  .,S 


*  JF 


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c< 


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^  **5 


M- 


c  y 


.m 


^■v  -•, 


V  V^% 


Iv  .  ^ 


:C'-- 


*V! 


^'.  ,  A- 


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f'fca.’ 


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ii>v  (1 


ir 


Tl 


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wfA- 


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r- 


iVA/t* 


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fjt" 


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N* 


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Li 


Table  A  — Average  Groivtli  of  451  Seqrioia  Trees  in  California, 
of  the  Life  of  the  Trees,  beginning  xolth  their 


,  bi/  Decades  and  Centuries 
Youth. 


[This  table  is  the  basis  of  the  Corrective  Factor  for  Age,  shown  in  figures  35  and  36,  and  first  column  of  Table  E.] 


Ago  of 
trees  in 
years. 

*  No.  of 
measure¬ 
ments. 

Average 

growth. 

Age  of 
trees  in 
years. 

*  No.  of 
measure¬ 
ments. 

Average 

growth. 

Age  of 
trees  in 
years. 

*  No.  of 
measure¬ 
ments. 

Average 

growth. 

Age  of 
trees  in 
;  years. 

*  No.  of 
measure¬ 
ments. 

Average  1 
growth.  1 

Age  of 
trees  in 
years. 

*  No.  of 
measure¬ 
ments. 

Average 

growth. 

1-10 

635 

myn. 

27.50 

111-120 

777 

mm. 

21,81 

221-230 

777 

mm, 

23.20 

1051-1150 

5,752 

mm. 

8.70 

2151-2250 

689 

7?i7n. 

7.55 

11-20 

644 

26.16 

121-130 

780 

21.96 

231-240 

777 

20.91 

1151-1250 

5,314 

8,38 

2251-2350 

514 

7..37 

21-30 

657 

23..S7 

131-140 

781 

22.08 

241-250 

777 

20.40 

1251-1350 

4,569 

8.10 

2351-2450 

280 

7.63 

31-40 

666 

22.23 

141-1.50 

781 

22.10 

251-350 

7,779 

20.11 

1351-1450 

3,992 

8.08 

2451-2550 

110 

6.91 

41-50 

676 

21. ,52 

1.51-160 

781 

22.31 

351-450 

7,700 

15.41 

14.51-15.50 

3,503 

7.87 

2551-2650 

110 

6.95 

51-60 

684 

21.27 

161-170 

783 

22.10 

451-,550 

7,485 

12.13 

1.551-1650 

2,991 

7.60 

2651-2750 

110 

7..50 

61-70 

6.87 

21.05 

171-180 

783 

22.08 

551-650 

6,922 

11.90 

1651-1750 

2,521 

7.48 

2751-2850 

60 

6.84 

71-80 

690 

21.05 

181-190 

783 

21.91 

651-750 

6,911 

10.32 

'  1751-1850 

2,186 

7.62 

2851-2950 

40 

6.38 

81-90 

695 

21.03 

191-200 

783 

21.91 

751-8.50 

6,605 

9.88 

1851-1950 

1,721 

7.95 

2951-3050 

30 

5.43 

91-100 

772 

21.60 

201-210 

784 

21.89 

851-950 

6,426 

9.44 

,  1951-20.50 

1,424 

7.89 

3051-3150 

20 

5,60 

101-110 

777 

21.72 

211-220 

784 

21.28 

951-10.50 

6,168 

9.02 

'  20.51-2150 

1,196 

8.03 

3151-.3250 

18 

6.70 

*  This  means  the  total  number  of  groups  of  rings  upon  which  the  figures  are  based.  Each  group  contains  10  rings. 


Table  B. — Comparative  Growth  of  Short-lived  and  Long-lived  Sequoias,  by  Groups;  Corrective 

Factor  for  Longevity.  (See  figure  37.) 


Group. 

First  250  years  of  life. 

250  to  650  years 
of  age. 

650-1050  years 
of  age. 

1050- 

L450  years  of 
age. 

1450-1850  years 
of  age. 

1  0-1050  years  of  age. 

*  Basis 
in 

decades. 

*  Total 
grow'th. 

Average 

growth. 

Basis  in 
decades. 

Total 

growth. 

Average 

growth. 

Basis  in 
decades. 

Total 

growth. 

Average 

growth. 

Basis  in 
decades. 

Total 

growth. 

Average  ' 

growth. 

Basi.s  in 
decades. 

Total 

growth. 

j  Average 

1  growth. 

Basis  in 
decades. 

Total 

growth. 

Average 

growth. 

1 

173 

3, .583 

20  72 

. 

2 

198 

3,485 

8  1Q.5 

17  61 

3 

351 

1  6.54 

29  33 

4 

42  .370 

2.5  60 

. 

5 

.541 

12,278 
fi  478 

22  60 

834 

1 3  782 

16  .51 

0 

9.Ft7 

25.21 
23  43 

400 

680 

.5  QQl 

14  77 

7 

433 

in  227 

in  *?14 

1.5  21 

g 

7*^f> 

1 5 

21  07 

1  6  0.*44 

1-5  31 

. 

9 

1  024 

92  n7R 

21  ,5.'^ 

1  680 

27  220 

IB  90 

1  664 

18  781 

11.31 

4,384 

68,077 

1.5.52 

10 

1  OnQ 

26,015 

40  331 

24  60 

1  680 

2.5  881 

1.5  42 

1  680 

18  021 

10.72 

4,419 

62,917 

15.80 

Li 

li899 

21  23 

3  non 

48!405 
38  466 

16  11 

.•^[oon 

33  882 

11  30 

7,899 

122,618 

1.5.55 

1  6  30 

2  .^60 

26  786 

1 1  32 

. 

6,130 

100,976 

16.35 

13 

1,237 

26406 

21.32 

1,960 

28(580 

14.57 

lioeo 

18457 

9.40 

1,948 

17,008 

8.73 

5,157 

73,443 

14.21 

9  040 

10  116 

0  87 

78,475 

14.73 

15 

1,187 

24,040 

.  10 

20.28 

1,880 

24,459 

13.01 

1,880 

16,733 

8.90 

L880 

15441 

8.23 

4,947 

65,232 

13.21 

16 

755 

14,489 

19.20 

1,320 

18,054 

13.67 

1,320 

12,179 

9.22 

1,320 

10,468 

7.93 

3,395 

44,722 

13.18 

17 

1,133 

26,303 

22.35 

1,880 

25,905 

13.78 

1,880 

15,479 

8.23 

1,880 

13,427 

7.15 

1,866 

12,692 

6.80 

4,893 

67,687 

13.82 

18 

707 

14,159 

20.05 

1,200 

16,317 

13.61 

1,200 

10,220 

8.52 

1,200 

8,936 

7.44 

1,200 

9,3,89 

7.82 

3,107 

40,696 

13.09 

19 

649 

12,142 

18.75 

1,000 

15,087 

15.09 

1,000 

8,300 

8.30 

1,000 

8,221 

8.22 

1,000 

8,396 

8.40 

2,649 

35,529 

13.40 

20 

1,223 

21,039 

17.22 

1,960 

29,432 

15.01 

1,960 

17,566 

8.97 

1,960 

15,337 

7.84 

1,960 

15,288 

7.80 

5,143 

68,037 

13.24 

21 

376 

7,200 

19.15 

680 

10,041 

14.78 

680 

5,518 

7.63 

680 

4,880 

7.18 

680 

5,072 

7.47 

1,736 

22,759 

13.10 

22 

587 

14,030 

23.92 

960 

12,475 

12.98 

960 

8,077 

8.42 

960 

6,451 

6.72 

960 

6,925 

7.22 

2,507 

.i4,582 

13.77 

23-25 

355 

5,899 

16.61 

680 

9,069 

13.36 

680 

5,364 

7.89 

680 

4,300 

6.33 

680 

4,835 

7.12 

1,715 

20,332 

11.83 

26-31 

271 

4,564 

16.86 

440 

6,066 

13.80 

440 

3,207 

7.30 

440 

2,997 

6.78 

440 

2,631 

5.98 

1,151 

13,837 

12.02 

9-12 

1,937 

5,392 

124,166 

23.08 

8,720 

1,39,972 

16.05 

1 

4,416 

3,762 

73,643 

21-31 

1,589 

31,693 

20.03 

2,760 

37,651 

_ 

_ 

0 

1  >* 

c  i  y 

■SsSh 

b 

■a  ^'0 

0  ©  ly 

£  T3  M 

>• 

§  &  .S 

2  C3  ^3 

0  a.5 

C  eO  a 
CO 

w  o-“  g 

15.70 

1.00 

15.70 

1.00 

15.70 

1.00 

15.70 

1.00 

15.70 

1.00 

15.70 

1.00 

15.70 

1.00 

15.70 

1.00 

15.05 

1.002 

15.60 

1.005 

15.40 

1.02 

1.5.15 

1.0,35 

14.90 

1.05 

14.60 

1.075 

14.30 

1.095 

14.00 

1.12 

13.75 

1.14 

13.50 

1.16 

13.25 

1.185 

13.00 

1.205 

12.75 

1.23 

12.50 

1.255 

t23 

12.30 

1.275 

24 

12.15 

1.29 

25 

12.00 

1.31 

26 

11.90 

1.32 

27 

11.90 

1.32 

28 

11.90 

1.32 

29 

11.90 

1.32 

30 

11.90 

1.32 

31 

11.90 

1.32 

) 


*  The  first  column  shows  the  total  number  of  decades  for  all  the  trees  of  the  total  growth, 

decades  are  available  for  one  tree,  the  inner  decade  bcins  rotted  away,  23  for  another,  and  or  a  lire ,  e  .  ' 

t  Numbers  of  later  groups,  which  here  arc  separated  in.stcad  of  being  combined  .as  in  earlier  columns. 


301 


That  is,  if  24 


302 


Table  C. — List  of  Individual  Sequoia  Trees  measured  in  California  in  1911  and  1912. 


1  Group.  II 

Place. 

(See  note  at  end  of 
table,  p.  307.) 

First  year* 

of  tree. 

Year*  of 

cutting. 

Age  of  tree 

at  cutting. 

Last  decade 

measured. 

No.  of 

readings. 

Difference  between 
readings. 

Readings  to 
be  used. 

Decades  to  be  added  and  intervala. 

j  A&B. 

d 

•0 

< 

Q 

"8 

<! 

j  A&E. 

A. 

B. 

c. 

D.  E. 

1 

A. 

B. 

c. 

D, 

E. 

Dec. 

Int. 

Deo. 

Int. 

Deo. 

Int. 

Deo. 

Int. 

Dec. 

Int. 

8 

Millwood . 

983a 

1884a 

901 

1871-1880 

1 

_ 

X 

_ 

_ 

_ 

1 

450 

_ 

_ 

_ 

— 

— 

— 

18 

Do  . 

606 

1884 

1944 

1871-1880 

1 

— 

— 

— 

— 

X 

— 

— 

3 

500 

— 

— 

— 

— 

— 

— 

— 

— 

12 

Do  . 

560a 

1884 

1324 

1871-1880 

2 

9 

— 

— 

— 

X'X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

— 

12 

Do  . 

531a 

1884 

1353 

1871-1880 

2 

23 

— 

— 

— 

X 

X 

— 

2 

440 

0 

— 

— 

— 

— 

— 

— 

— 

10 

2013 

1R71  Iftsn 

1 

, 

V 

_ 

. 

3 

500 

_ 

19 

TOn 

2026 

i«7i  iftftn 

1 

V 

3 

500 

14 

Boule . 

371o 

1904 

1533 

1891-1900 

2 

16 

— 

— 

X 

X 

— 

— 

_ 

2 

510 

0 

— 

— 

— 

— 

— 

— 

— 

10 

Do . 

705a 

1904 

1199 

1891-1900 

2 

1 

— 

— 

— 

X 

X 

— 

— 

_ 

0 

— 

0 

— 

— 

— 

— — 

— 

— 

— 

4 

Do . 

1304a 

1904 

600 

1891-1900 

1 

5 

Do . 

1287a 

1904 

617 

1891-1900 

1 

4 

Do . 

1313a 

1904 

591 

1891-1900 

1 

1 

Do . 

1618a 

1904 

286 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

— 

— 

13 

Do . 

438a 

1904 

1466 

1891-1900 

3 

2 

18 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

— 

— 

8 

Do . 

9240 

1904 

980 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

_ 

1 

480 

— 

— 

— 

— 

— 

— 

— 

— 

20 

Do . 

2856 

1904 

2190 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

4 

400 

— 

— 

— 

— 

— 

— 

— 

— 

9 

Converse  Rob  Roy. 

815a 

1904 

1089 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

1 

540 

— 

— 

— 

— 

— 

— 

— 

— 

19 

Boule . 

6 

1904 

1891-1900 

.... 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

21 

Do . 

6 

1904 

1891-1900 

.... 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

4 

Do . 

13180 

1904 

586 

1891-1900 

1 

— 

— 

3 

Do . 

14120 

1904 

492 

1891-1900 

1 

7 

Converse  Rob  Roy. 

1014a 

1904 

890 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

450 

— 

— 

— 

— 

— 

— 

— 

— 

9 

Indian  Basin . 

885o 

1903 

1018 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

500 

— 

— 

— 

— 

— 

— 

— 

— 

8 

Do  . 

907o 

1904 

997 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

500 

— 

— 

— 

— 

— 

— 

— 

— 

1 

Converse  Rob  Roy. 

1646u 

1906 

260 

1901-1910 

1 

_ 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

— 

— 

7 

Do 

1015a 

1904 

889 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

1 

450 

— 

— 

— 

— 

— 

— 

— 

— 

4 

Boule . 

1363a 

1906 

543 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

— 

— 

9 

Converse  Rob  Roy. 

840a 

19067 

1066 

1861-1870 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

530 

— 

— 

— 

— 

— 

— 

— 

— 

5 

Do 

1237a 

1906 

669 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

330 

— 

— 

— 

— 

— 

— 

— 

— 

17 

Do 

86o 

1904 

1818 

1891-1900 

4 

85 

78 

94 

— 

— 

X 

— 

X 

— 

— 

— 

0 

— 

— 

— 

0 

— 

— 

— 

15 

Do 

247o 

1906 

1659 

1901-1910 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

3 

420 

— 

— 

— 

— 

— 

— 

— 

— 

22 

Converse  T.  8 . 

4736 

1906 

2379 

1891-1900 

5 

14 

34 

56 

73 

— 

X 

— 

X 

— 

— 

— 

4 

460 

— 

— 

0 

— 

— 

— 

15 

Converse  Hoist .... 

225a 

1906 

1681 

1891-1900 

5 

50 

55 

164 

175 

— 

— 

— 

X 

X 

— 

— 

— 

— 

— 

— 

1 

840 

0 

— 

14 

Converse  T.  S . 

388a 

1906 

1518 

1901-1910 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

2 

510 

— 

— 

— 

— 

— 

— 

— 

— 

13 

Converse  H . 

418a 

1906 

1488 

1901-1910 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

2 

490 

— 

— 

— 

— 

— 

— 

— 

— 

10 

Converse  T.  S . 

704a 

1904 

1200 

1891-190C 

2 

7 

— 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

600 

— 

— 

— 

— 

— 

— 

5 

Indian  Basin . 

1247a 

1904 

657 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

330 

— 

— 

— 

— 

— 

— 

— 

— 

15 

Do  . 

210o 

1904 

1694 

1891-1900 

2 

14 

— 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

850 

— 

— 

— 

— 

— 

— 

5 

Do  . 

12850 

1904 

619 

1891-1900 

1 

X 

0 

4 

Do  . 

1359a 

1904 

545 

1891-1900 

1 

X 

0 

19 

Do  . 

1396 

1904 

2043 

1891-1900 

4 

no 

121 

16 

— 

— 

X 

X 

— 

— 

— 

— 

1 

1000 

0 

— 

— 

— 

— 

— 

4 

Do  . 

13510 

1904 

553 

1891-1900 

1 

X 

0 

14 

Do  . 

354a 

1906 

1552 

1901-1910 

3 

26 

14 

— 

— 

X 

— 

X 

— 

— 

0 

— 

— 

— 

0 

— 

— 

— 

— 

— 

4 

Do  . 

1377a 

1904 

531 

1891-1900 

1 

X 

0 

5 

Do  . 

1256a 

1904 

648 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

320 

— 

— 

— 

- - 

— 

— 

— 

8 

Do  . 

935  7o 

1904 

969 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

480 

— 

— 

— 

— 

— 

— 

— 

— 

14 

Do  . 

387o 

1904 

1519 

1891-1900 

2 

4 

— 

— 

— 

X 

X 

— 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

— 

— 

4 

Do  . 

1362a 

1904 

542 

1891-1900 

1 

X 

0 

11 

Drt 

9! 

1? 

1 

12 

Do  . 

513a 

1904 

1391 

1891-1900 

1 

— 

— 

_ 

X 

— 

— 

— 

1 

650 

_ 

_ 

_ 

_ 

_ 

— 

_ 

9 

Do  . 

904a 

1904 

1000 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

400 

— 

— 

— 

— 

— 

— 

— 

— 

13 

Do  . 

417a 

1904 

1487 

1891-1900 

3 

38 

45 

— 

— 

— 

X 

X 

— 

— 

— 

— 

1 

7.50 

0 

— 

— 

— 

— 

— 

15 

Do  . 

240o 

1904 

1664 

1891-1900 

3 

31 

26 

— 

— 

X 

X 

— 

— 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

13 

Do  . 

4110 

1904 

1493 

1891-1900 

2 

10 

— 

— 

— 

X 

X 

— 

— 

— 

1 

750 

0 

9 

Do  . 

894a 

1904 

1010 

1891-1900 

3 

5 

3 

— 

— 

X 

X 

X 

— 

— 

0 

— 

0 

— 

0 

— 

— 

- - 

— 

— 

13 

Do  . 

436a 

1904 

1468 

1891-1900 

3 

23 

29 

— 

— 

— 

X 

X 

— 

— 

— 

— 

1 

730 

0 

— 

— 

— 

— 

— 

13 

Do  . 

439a 

1904 

1465 

1891-1900 

2 

7 

— 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

730 

— 

— 

— 

— 

— 

— 

12 

Do  . 

538a 

1904 

1366 

1891-1900 

3 

2 

8 

— 

— 

X 

X 

X 

— 

— 

0 

— 

0 

— 

1 

600 

— 

— 

— 

— 

5 

Do  . 

1284a 

1904 

620 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

310 

— 

— 

— 

— 

— 

— 

— 

— 

19 

Do  . 

1216 

1904 

2025 

1891-1900 

2 

4 

— 

— 

— 

X 

X 

— 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

— 

19 

Do  . 

1126 

1904 

2016 

1891-1900 

3 

20 

175 

— 

— 

X 

X 

— 

— 

— 

2 

650 

0 

9 

Do  . 

S68a 

1904 

1036 

1891-1900 

3 

2 

3 

— 

— 

X 

X 

X 

— 

— 

0 

— 

0 

— 

0 

— 

— 

— 

— 

— 

6 

Do  . 

1188a 

1904 

716 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

1 

360 

— 

— 

— 

— 

— 

— 

— 

— 

22 

Converse  Mill . 

4456 

1901 

2346 

1891-1900 

4 

40 

1 

59 

— 

X 

X 

X 

— 

— 

0 

4 

460 

3 

580 

— 

— 

... 

20 

Converse  H . 

2386 

1891 

2129 

1881-1890 

2 

1 

— 

— 

— 

X 

X 

— 

— 

— 

0 

0 

— 

— 

— 

— 

— 

— 

— 

20 

Do  . 

2146 

1901 

2115 

1891-1900 

4 

18 

10 

28 

— 

X 

X 

X 

— 

— 

0 

— 

3 

500 

1 

1050 

— 

— 

— 

— 

20 

Do  . 

2856 

1891 

2176 

1881-1890 

2 

69 

— 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

19 

Do  . 

1606 

1891 

2051 

1881-1890 

1 

— 

— 

— 

— 

X 

— 

— 

— 

— 

3 

500 

- - 

— 

— 

— 

— 

— 

— 

— 

21 

Do  . 

3746 

1904 

2278 

1891-1900 

3 

13 

14 

— 

— 

X 

X 

X 

— 

— 

2 

750 

0 

— 

0 

— 

— 

— 

— 

— 

18 

Do  . 

106 

1904 

1914 

1891-1900 

3 

19 

19 

— 

— 

— 

X 

X 

— 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

20 

Converse,  T.  S.  .  .  . 

2716 

1901 

2172 

1891-1900 

3 

75 

65 

— 

— 

— 

X 

X 

_ 

_ 

— 

— 

0 

— 

1 

1100 

— 

— 

— 

— 

18 

Converse  H . 

266 

1904 

1930 

1891-1900 

3 

38 

32 

— 

— 

— 

X 

X 

— 

_ 

— 

— 

0 

— 

0 

— 

— 

— 

_ 

22 

Do  . 

4596 

1892 

2351 

1881-1890 

3 

0 

12 

— 

— 

X 

X 

X 

— 

0 

— 

0 

— 

1 

1170 

— 

— 

— 

C  &  D 

C  &  E 

22 

Converse,  W.  F. . . . 

4676 

1892 

2359 

1881-1890 

3 

39 

9 

— 

— 

— 

— 

X 

— 

X 

— 

— 

— 

— 

0 

— 

— 

_ 

0 

31 

Converse  H . 

13186 

1892 

3210 

1881-1890 

4 

68 

62 

38 

— 

— 

X 

— 

X 

— 

— 

— 

0 

— 

— 

— 

3 

800 

— 

— 

2 

■Ho 

0 

20 

Do  . 

2206 

1902 

2122 

1881-1890 

3 

15 

128 

_ 

_ 

X 

_ 

_ 

__ 

___ 

0 

_ 

_ 

18 

Do  . 

356 

1902 

1937 

1891-1900 

3 

14 

12 

— 

— 

X 

X 

X 

— 

— 

1 

900 

0 

— 

0 

— 

_ 

_ 

- - 

10 

Indian  Basin . 

730o 

1902 

1172 

1891-1900 

3 

8 

3 

— 

— 

X 

X 

X 

— 

— 

0 

— 

1 

580 

0 

— 

— 

— 

— 

— 

3 

Do  . 

1484a 

1904 

420 

1891-1900 

1 

— 

— 

— 

— 

X 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

— 

— 

9 

Dn 

1903 

0 

17 

Do  . 

22o 

1903 

1881 

1891-1900 

3 

15 

19 

_ 

_ 

X 

X 

_ 

_ 

0 

0 

_ 

_ 

17 

Do  . 

57a 

1902 

1845 

1891-1900 

3 

6 

2 

— 

— 

X 

X 

X 

— 

— 

0 

— 

1 

800 

0 

— 

— 

— 

— 

— 

3 

Dn 

11 

Do  . 

601  o 

1903 

1302 

1891-1900 

3 

6 

4 

_ 

— 

X 

X 

X 

_ 

_ 

1 

650 

0 

_ 

0 

_ 

_ 

11 

Do  . 

663a 

1903 

1240 

1891-1900 

3 

9 

3 

— 

— 

X 

X 

X 

— 

— 

0 

— 

1 

620 

0 

_ 

— 

— 

— 

— 

10 

Do  . 

761a 

1903 

1142 

1891-1900 

3 

16 

8 

— 

— 

X 

— 

X 

— 

— 

1 

560 

_ 

0 

_ 

_ 

— 

3 

r>n 

1486a 

1903 

417 

1891-1900 

0 

1 

1 

2 

3 

4 

5 

6 

7 

8 
9 

10 

11 

12 

13 

14 

15 

16 
S 
18 

19 

20 
21 
22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 
61 
62 

63 

64 

65 

66 

67 

68 

69 

70 

71 

72 

73 

74 

75 

76 

77 

78 

79 

80 
81 
82 

83 

84 

85 

86 
87 


•  A.  D.  is  indicated  by  o;  B.  C.  by  5. 


Table  C. — Individual  Sequoia  Trees  measured  in  California  in  1911  and  1912 — Continued.  303 


Differences  between 

Headings  ] 

Decades  to  be  added  and  intervals 

§■ 

cS  . 

0  0 

'S  M) 

.  0 

*0  e 

CO 

•S  g 

readings. 

to  be  used. 

between  them. 

No. 

5 

Place. 

S'S 

6^ 

u 

>2  'S 

d 

d 

A 

B. 

C 

D. 

rT  0 

5 

bD  ^ 

J  ^ 

•a 

■a 

•0 

k. 

B. 

[1. 

a. 

A 

< 

< 

Dec. 

Int. 

Oec. 

Int. 

Dec. 

Int. 

Dec. 

Int. 

88 

2 

Indian  Basin. . . . 

15150 

1903 

388 

1891-1900 

1 

_ 

_ 

_ 

X- 

0 

_ 

- 

- 

_ 

89 

5 

Do  . 

1202o 

1905 

703 

1891-1900 

1 

_ _ 

_ 

_ 

X 

1 

350 

- 

— 

_ 

X 

11 

620a 

1864 

1244 

1851-1860 

\ 

— 

X 

0 

_ 

_ 

_ 

__ 

. 

90 

2 

Indian  Basin .... 

1504a 

1903 

399 

1891-1900 

1 

— 

— 

— 

X- 

0 

— 

— 

— 

— 

— 

— 

— 

91 

12 

Do 

5850 

1903 

1318 

1891-1900 

3 

6 

6 

— 

X 

X 

X 

0 

— 

— 

— 

— 

— 

— 

— 

92 

17 

Do 

17o 

1903 

1886 

1891-1900 

3 

4 

— 

— 

X 

X 

0 

— 

— 

— 

— 

— 

— 

— 

93 

3 

Do 

1406a 

1903 

497 

1891-1900 

1 

— 

— 

— 

X 

0 

— 

— 

— 

— 

— 

— 

— 

94 

3 

Do 

1416a 

1903 

487 

1891-1900 

1 

— 

— 

X 

0 

— 

— 

— 

— 

— 

— 

— 

95 

2 

Do 

I6OO0 

1903 

303 

1891-1900 

1 

— 

— 

— 

X 

0 

— 

— 

— 

— 

— 

— 

— 

96 

15 

Do 

200a 

1903 

1703 

1891-1900 

4 

17 

12 

41 

X 

X 

— 

— 

2 

550 

— 

— 

0 

— 

97 

16 

Do 

151a 

1903 

1762 

1891-1900 

1 

- - 

— 

— 

X 

2 

600 

— 

— 

— 

— 

— 

— 

98 

99 

21 

3305 

1902 

2232 

1891-1900 

2 

4 

— 

_ 

X 

X 

0 

_ 

0 

— 

— 

_ 

— 

— 

14 

Converse  W.  F.. . 

307a 

1902 

1595 

1891-1900 

4 

31 

15 

23 

X 

X 

— 

— 

— 

1 

800 

0 

— 

100 

14 

Do 

309o 

1902 

1593 

1891-1900 

3 

41 

46 

— 

X 

0 

101 

22 

Do 

4376 

1902 

2339 

1891-1900 

4 

51 

37 

62 

— 

X 

— 

X 

— 

- - 

0 

— 

— 

— 

1 

1200 

102 

20 

2036 

1902 

2105 

1891-1900 

3 

23 

2 

— 

X 

X 

X 

— 

2 

700 

0 

— 

2 

700 

— 

— 

103 

11 

Do  .... 

615a 

1902 

1287 

1891-1900 

3 

4 

11 

— 

X 

X 

X 

_ 

0 

— 

0 

— 

0 

— 

— 

— 

104 

17 

Do  .... 

3a 

1902 

1899 

1891-1900 

2 

4 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

105 

20 

Converse  W.  F.. . 

2586 

1892 

2150 

1881-1890 

3 

33 

24 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

1100 

— 

— 

106 

22 

Do 

4666 

1892 

2358 

1881-1890 

3 

129 

89 

— 

— 

X 

X 

— 

— 

— 

0 

— 

4 

470 

— 

— 

107 

4 

Do 

1344a 

1892 

548 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

108 

4 

1369o 

1892 

523 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

109 

5 

Do  .... 

1206a 

1892 

686 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

1 

.340 

— 

— 

— 

— 

— 

110 

6 

Indian  Basin .... 

11510 

1903 

752 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

1 

370 

— 

— 

— 

— 

— 

— 

111 

6 

Do 

1109a 

1903 

794 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

1 

400 

— 

— 

— 

— 

— 

— 

112 

2 

Do 

I52O0 

1903 

383 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

■ — 

— 

— 

— 

113 

3 

Do 

14230 

1903 

480 

1891-1900 

1 

900 

114 

17 

36a 

1888 

1852 

1871-1880 

3 

25 

12 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

— 

— 

115 

17 

Do  . 

30a 

1888 

1858 

1871-1880 

3 

34 

6 

— 

X 

— 

X 

— 

0 

— 

— 

— 

0 

— 

— 

- - 

116 

29 

11916 

1876 

3067 

1861-1870 

4 

480 

71 

541 

X 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

117 

11 

Do  . 

614a 

1892 

1278 

1881-1890 

2 

5 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

118 

18 

Do  . 

946 

1893 

1987 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

1 

500 

— 

— 

— 

— 

— 

— 

119 

120 

21 

Do  . 

3006 

1890 

2190 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

4 

440 

— 

— 

— 

— 

— 

— 

19 

Do  . 

1536 

1893 

2046 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

3 

500 

— 

— 

— 

— 

— 

— 

121 

4 

Do  . 

13320 

1893 

561 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

122 

16 

186a 

1896 

1710 

1881-1890 

2 

30 

— 

— 

X 

X 

— 

0 

400 

3 

— 

— 

— 

— 

— 

123 

26 

Do  . 

8696 

1906 

2775 

1891-1900 

2 

17 

— 

— 

X 

X 

— 

— 

0 

900 

0 

— 

— 

— 

— 

— 

124 

25 

Do  . 

7206 

1906 

2626 

1891-1900 

2 

41 

— 

— 

X 

X 

— 

— 

0 

— 

4 

520 

— 

— 

— 

— 

125 

13 

Do  . 

437a 

1906 

1469 

1901-1910 

1 

— 

— 

— 

X 

— 

— 

— 

2 

490 

— 

— 

— 

— 

— 

— 

126 

13 

Do  . 

447a 

1906 

1459 

1901-1910 

1 

— 

— 

X 

— 

— 

— 

2 

490 

— 

— 

— 

— 

— 

— 

127 

128 
129 

18 

22 

11 

Do  . 

226 

1906 

1928 

1891-1900 

2 

26 

— 

— 

X 

X 

— 

— 

0 

480 

3 

— 

— 

— 

— 

— 

4376 

687o 

1895 

1893 

2332 

1881-1890 

1 

— 

— 

— 

X 

• — 

4 

460 

— 

— 

— 

— 

— 

— 

1206 

1881-1890 

0 

2 

130 

131 

13 

448a 

1893 

1445 

1881-1890 

2 

25 

— 

— 

X 

X 

— 

— 

0 

— 

3 

360 

— 

— 

— 

13 

478o 

1893 

1415 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

470 

— 

— 

— 

— 

— 

— 

132 

16 

Do . 

181a 

1893 

1712 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

570 

— 

— 

— 

— 

— 

133 

14 

Do . 

306a 

1893 

1587 

1881-1890 

2 

28 

— 

— 

X 

X 

— 

— 

0 

— 

3 

530 

— 

— 

— 

134 

135 

1 

Do . 

1643a 

1893 

250 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

15 

Do . 

247a 

1893 

1646 

1881-1890 

2 

8 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

136 

16 

Do . 

179o 

1890 

1711 

1881-1890 

2 

35 

— 

— 

X 

— 

— 

— 

0 

* - 

— 

— 

— 

— 

137 

16 

Do . 

197o 

1890 

1693 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

570 

— 

— 

138 

8 

Do . 

9290 

1890 

961 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

1 

480 

370 

139 

6 

Do . 

II4O0 

1890 

750 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

1 

— 

— 

— 

140 

13 

Do . 

473o 

1890 

1417 

1881-1890 

2 

21 

— 

— 

X 

X 

— 

— 

470 

0 

— 

141 

15 

225a 

1906 

1681 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

2 

560 

— 

— 

142 

143 

17 

Do  . 

1903 

1843 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

3 

460 

— 

— 

15 

Do  . 

227a 

1903 

1676 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

2 

560 

144 

16 

Do  . 

2OO0 

1903 

1703 

1891-1900 

1 

— 

— 

■ - 

X 

— 

— 

— 

3 

430 

145 

19 

Do  . 

1556 

1904 

2059 

1667 

1891-1900 

1 

— 

— 

— 

X 

— 

3 

500 

— 

146 

15 

8 

Do  . 

237a 

1904 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

2 

550 

147 

Do  . 

928a 

1904 

976 

1891-1900 

1 

— 

— 

— 

X 

— * 

— 

1 

1 

2 

490 

148 

149 

8 

15 

Do  . 

Do  . 

925a 

220a 

1904 

1896 

979 

1676 

1891-1900 

1881-1890 

1 

1 

_ 

— 

— 

X 

X 

— 

— 

400 

560 

— 

— 

— 

— 

— 

— 

150 

151 

152 

153 

154 

155 

156 

157 

158 

159 

160 
161 
162 

163 

164 

165 

166 
167 

15 

5 

272o 

1898 

1626 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

2 

560 

0 

Do  . 

1260a 

1898 

638 

1881-1890 

2 

1 

— 

— 

X 

X 

— 

— 

0 

0 

— 

6 

Do  . 

1130a 

1900 

770 

1891-1900 

2 

1 

— 

— 

X 

X 

— 

0 

8 

11 

17 

18 

12 

12 

12 

8 

8 

8 

9 

8 

1 

Do  . 

907a 

1900 

993 

1891-1900 

2 

0 

— 

— 

X 

X 

0 

0 

430 

Do  . 

603a 

1900 

1307 

1891-1900 

2 

26 

— 

— 

X 

X 

— 

— 

0 

560 

1000 

2 

Do  . 

217a 

1904 

1687 

1891-1900 

1 

— 

— 

'  - 

X 

— 

2 

Do  . 

966 

1904 

2000 

1891-1900 

1 

— 

— 

— 

X 

1 

1 

670 

Do  . 

563a 

1909 

1346 

1901-1910 

2 

15 

— 

— 

X 

X 

1 

0 

450 

350 

470 

490 

Do  . 

S49a 

1909 

1360 

1901-1910 

1 

— 

— 

— 

X 

1 

2 

Do  . 

596a 

1909 

1313 

1901-1910 

1 

— 

— 

- - 

X 

1 

1 

1 

1 

1 

Do  . 

972a 

1909 

937 

1901-1910 

1 

— 

— 

— 

X 

Do  . 

928a 

1909 

981 

1901-1910 

1 

— 

— 

— 

X 

j”” 

1 _ _ 

Do  . 

915a 

1909 

994 

1901-1910 

1 

— 

— 

— 

X 

500'  — 

1 

Do  . 

893a 

1909 

loie 

1901-1910 

1 

— 

— 

— 

X 

X 

X 

X 

! 

Do  . 

905a 

1909 

1004 

1901-1910 

1 

— 

— 

— 

1 

__ 

1671a 

1906 

23£ 

1891-1900 

1 

— 

— 

— 

1“ 

1 

Do . 

1681a 

1906 

22£ 

1891-1900 

1 

— 

— 

X 

0 

— 

_ 

11 

Do . 

689a 

1905 

12ie 

1891-1900 

2 

3 

X 

168 

169 

170 

171 

172 

173 

174 

”12" 

7 

597a 

1900 

130£ 

1891-1900 

2 

24 

— 

X 

X 

400 

340 

1086a 

1885 

79t 

1871-1880 

1 

— 

1 

0 

_ 

_ 

5 

Do  , . . . 

1206a 

1885 

671 

1871-1880 

1 

— 

_ 

r  — 

_ 

7 

Do  .... 

1059a 

1885 

826 

1871-1880 

1 

— 

X 

X 

650 

, 

- 

— 

12 

21 

Do  .... 

SOOa 

1885 

129£ 

1871-1880 

1 

— 

4 

440 

— 

Do  .... 

3541 

1902 

225( 

1891-1900 

2 

40 

X 

>< 

304 


Table  C. — Individual  Sequoia  Trees  measured  in  California  in  1911  and  1912 — Continued. 


Cu 

irst  year 
j{  tree. 

'o  M 
u-  .3 

^  a 

M'S 

°  i 

Difference  between 
readings. 

Readings 
to  be  used 

Decades  to  be  added  and  intervals 
between  them. 

No. 

P 

o 

O 

Place. 

®  p 

O  V 

T3  TO 

O  'TS 
es 

n 

d 

Q 

A. 

B. 

c. 

D. 

A. 

B. 

D. 

Ph 

<  n 

<5 

< 

«8 

<! 

Dec 

Int. 

Dec 

Int 

Dec 

Int 

Dec. 

Int. 

175 

10 

Dillonwood . 

130a 

1903 

1776 

1891-1900 

2 

240 

_ 

_ 

b 

ot 

1 

used 

170 

10 

Do  . 

190a 

1902 

1271 

1891-1900 

2 

11 

— 

— 

X 

X 

— 

1 

850 

0 

— 

— 

— 

— 

— 

177 

17 

Do  . 

49o 

1880 

1831 

1871-1880 

1 

— 

— 

— 

X 

— 

— 

— 

3 

430 

— 

— 

— 

— 

— 

— 

178 

10 

Do  . 

134a 

1900 

1766 

1891-1900 

2 

7 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

179 

13 

Do  . 

422a 

1910 

1488 

1901-1910 

2 

16 

— 

— 

X 

X 

— 

— 

0 

— 

2 

490 

— 

— 

— 

- - 

ISO 

20 

Do  . 

2756 

1910 

2181 

1901-1910 

2 

6 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

,  - 

— 

— 

181 

13 

Do 

480a 

1900 

1420 

1891-1900 

1 

— 

— 

— 

X 

— 

— 

— 

2 

470 

— 

— 

— 

— 

— 

— 

182 

14 

Do  . 

370a 

1900 

1530 

1891-1900 

1 

— 

— 

X 

— 

— 

— 

2 

510 

— 

— 

— 

_ 

— 

— 

183 

10 

Frasier . 

1810 

1903 

1707 

1891-1900 

2 

28 

— 

— 

X 

X 

— 

— 

3 

530 

0 

— 

— 

_ 

— 

— 

184 

16 

Do . 

193o 

1898 

1705 

1891-1900 

2 

15 

— 

— 

X 

X 

— 

— 

0 

530 

2 

— 

— 

— 

— 

— 

185 

13 

Dillonwood . 

442o 

1898 

1446 

1891-1900 

2 

7 

— 

— 

X 

X 

— 

— 

0 

- - 

0 

— 

— 

— 

— 

180 

13 

Do  . 

431a 

1888 

1457 

1881-1890 

2 

19 

— 

— 

X 

X 

— 

— 

0 

— 

2 

490 

— 

— 

— 

— 

187 

20 

Frasier . 

2886 

1888 

2176 

1881-1890 

2 

5 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

ISS 

15 

Do . 

252a 

1890 

1638 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

530 

— 

— 

— 

— 

— 

— 

189 

15 

Do . 

279a 

1890 

1611 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

530 

— 

— 

— 

— 

— 

— 

190 

16 

Enterprise . 

165a 

1893 

1728 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

3 

430 

— 

— 

— 

— 

— 

191 

15 

Do  . 

265a 

1893 

1628 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

530 

— 

— 

— 

— 

— 

— 

102 

23 

Do  . 

5336 

1893 

2426 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

4 

490 

— 

— 

— 

- - 

193 

23 

Do  . 

5446 

1893 

2437 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

4 

490 

— 

— 

— 

— 

— 

194 

23 

Do  . 

5686 

1893 

2461 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

2 

980 

— 

— 

— 

— 

— 

195 

29 

Do  . 

11416 

1893 

3034 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

— 

6 

370 

— 

— 

— 

_ 

— 

— 

190 

197-200 

26 

No  st 

Do  . 

atistics  for  these  Nos. 

8766 

1893 

2769 

1881-1890 

1 

— 

— 

— 

X 

— 

— 

2 

400 

— 

— 

— 

— 

— 

201 

10 

Hume . 

701a 

1911 

1210 

1901-1910 

4 

33 

45 

35 

— 

X 

X 

X 

— 

— 

1 

630 

0 

— 

1 

630 

202 

5 

Do . 

1290a 

1911 

621 

1901-1910 

3 

24 

29 

— 

— 

X 

X 

— 

— 

— 

0 

— 

0 

— 

— 

— 

203 

5 

Do . 

1205a 

1911 

706 

1901-1910 

3 

8 

15 

— 

— 

X 

X 

— 

— 

— 

1 

350 

0 

— 

— 

— 

204 

5 

Do . 

1189a 

1911 

722 

1901-1910 

2 

15 

— 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

205 

5 

Do . 

1228a 

1911 

683 

1901-1910 

1 

— 

— 

— 

X 

— 

— 

1 

350 

— 

— 

— 

— 

— 

200 

4 

Do . 

1379a 

1911 

532 

1901-1910 

2 

1 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

207 

3 

Do . 

14820 

1911 

429 

1901-1910 

2 

0 

— 

— 

X 

X 

— 

0 

0 

— 

— 

— 

— 

— 

208 

5 

Do . 

1217a 

1911 

694 

1901-1910 

2 

12 

— 

— 

X 

X 

— 

— 

0 

— 

1 

350 

— 

— 

— 

— 

209 

3 

Do . 

1482a 

1911 

429 

1901-1910 

2 

0 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

210 

6 

Do . 

1137a 

1911 

774 

1901-1910 

1 

0 

- - 

— 

X 

— 

— 

— 

1 

380 

— 

— 

— 

— 

— 

— 

211 

2 

Do . 

15780 

1911 

333 

1901-1910 

2 

2 

_ 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

212 

1 

Do . 

1620a 

1911 

291 

1901-1910 

2 

3 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

213 

6 

Do . 

1124a 

1911 

787 

1901-1910 

2 

15 

— 

— 

— 

X 

_ 

— 

— 

— 

0 

— 

— 

— 

— 

— 

214 

3 

Do . 

1463a 

1911 

448 

1901-1910 

2 

8 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

215 

9 

Comstock . 

896a 

1891 

995 

1881-1890 

2 

5 

— 

— 

X 

X 

— 

— 

0 

_ 

0 

— 

— 

— 

— 

— 

210 

17 

Do  . 

54a 

1891 

1837 

1881-1890 

2 

10 

— 

— 

X 

X 

— 

— 

0 

— 

1 

900 

— 

— 

— 

— 

217 

218 

4 

13 

Do  . 

Do  . 

13530 

481o 

1891 

538 

1881-1890 

2 

1 

0 

— 

— 

X 

N 

X 

ot 

d 

0 

— 

0 

— 

_ 

— 

— 

— 

219 

8 

Do  . 

9420 

1891 

949 

1881-1890 

3 

25 

3 

— 

X 

— 

— 

0 

— 

_ 

_ 

_ 

_ 

220 

7 

Do  . 

1026o 

1890 

864 

1881-1890 

2 

9 

— 

— 

X 

X 

— 

0 

— 

1 

420 

— 

— 

— 

— 

221 

222 

4 

4 

Do  . 

Do  . 

13180 

1314a 

1891 

1891 

573 

577 

1881-1890 

1881-1890 

3 

4 

11 

21 

31 

32 

— 

X 

N 

— ix!— 

0 

— 

— 

— 

1 

280 

— 

— 

223 

7 

Do  . 

1052a 

1891 

839 

1881-1890 

2 

6 

— 

X 

X 

— 

— 

0 

— 

0 

_ 

— 

_ 

_ 

_ _ 

224 

7 

Do  . 

1004a 

1891 

887 

1881-1890 

3 

19 

46 

— 

X 

0 

— 

225 

4 

Do  . 

13390 

1891 

552 

1881-1890 

2 

10 

— 

— 

X 

X 

— 

— 

1 

270 

0 

— 

— 

— 

— 

— 

220 

4 

Do  . 

1333a 

1891 

558 

1881-1890 

3 

10 

2 

— 

X 

X 

X 

— 

— 

— 

0 

— 

1 

270 

— 

— 

227 

4 

Do  . 

1294a 

1891 

597 

1881-1890 

4 

29 

8 

5 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

228 

4 

Do  . 

1348a 

1891 

543 

1881-1890 

2 

3 

— 

— 

X 

X 

— 

— 

0 

— 

0 

- - 

— 

— 

— 

229 

12 

Do  . 

516a 

1891 

1375 

1881-1890 

2 

3 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

230 

4 

Do  . 

1359a 

1891 

532 

1881-1890 

2 

4 

— 

— 

X 

X 

— 

— 

0 

- - 

0 

— 

— 

— 

— 

— 

231 

7 

Do  . 

1099o 

1891 

792 

1881-1890 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

2.32 

233 

9 

14 

Do  . 

Do  . 

839a 

1891 

1891 

1052 

1591 

1881-1890 

1881-1890 

4 

4 

10 

140 

1 

10 

20 

57 

X 

N 

X  X 

d 

0 

— 

1 

500 

0 

— 

— 

— 

2.34 

4 

Do  . 

13230 

1891 

568 

1881-1890 

2 

8 

X 

X 

_ 

0 

— 

0 

_ 

_ 

_ 

_ 

— 

235 

4 

Do  . 

13340 

1891 

557 

1881-1890 

2 

67 

— 

— 

— 

X 

_ 

— 

— 

— 

0 

— 

— 

— 

— 

— 

2.30 

8 

Do  . 

920a 

1891 

971 

1881-1890 

2 

9 

— 

— 

X 

X 

— 

— 

1 

480 

0 

— 

— 

— 

— 

— 

2.37 

8 

Do  . 

925a 

1891 

966 

1881-1890 

2 

17 

— 

— 

X 

X 

— 

— 

0 

— 

1 

300 

— 

— 

— 

— 

238 

4 

Do  . 

1344a 

1891 

547 

1881-1890 

2 

1 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

_ 

— 

— 

239 

18 

Do  . 

446 

1880 

1924 

1871-1880 

2 

24 

— 

— 

X 

X 

— 

— 

2 

630 

0 

— 

— 

— 

— 

— 

240 

15 

Do  . 

256a 

1891 

1634 

1881-1890 

3 

70 

3 

— 

X 

— 

— 

— 

0 

— 

— 

— 

— 

— 

— 

241 

3 

Do  . 

14620 

1891 

429 

1881-1890 

2 

3 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

242 

243 

4 

4 

Do  . 

Do  . 

1326a 

13490 

1891 

1891 

565 

542 

1881-1890 

1881-1890 

3 

3 

25 

27 

12 

69 

— 

X 

N 

X 

d 

0 

— 

— 

280 

— 

— 

244 

15 

Do  . 

264a 

1891 

1627 

1881-1890 

3 

63 

11 

— 

X 

X 

0 

— 

— 

.... 

1 

800 

_ 

— 

245 

4 

Do  . 

1355a 

1890 

535 

1881-1890 

3 

9 

1 

— 

X 

X 

X 

— 

1 

150 

0 

— 

1 

300 

— 

— 

240 

11 

Do  . 

657a 

1891 

1234 

1881-1890 

3 

,50 

21 

— 

X 

— 

X 

— 

0 

— 

— 

— 

2 

400 

— 

— 

247 

11 

Do  . 

602o 

1886 

1284 

1871-1880 

2 

2 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

- - 

248 

10 

Do  . 

751a 

1891 

1140 

1881-1890 

2 

10 

— 

— 

X 

X 

_ 

— 

0 

— 

1 

570 

— 

— 

— 

— 

249 

11 

Do  . 

611o 

1890 

1279 

1881-1890 

2 

10 

_ 

— 

X 

X| 

— 

0 

— 

1 

660 

— 

— 

— 

— 

250 

9 

Do  . 

803a 

1890 

1087 

1881-1890 

2 

0 

— 

— 

X 

x' 

0 

- - 

0 

— 

— 

— 

— 

— 

251 

9 

Do  . 

800 0 

1891 

1091 

1881-1890 

3 

19 

14 

— 

X 

_ 

X 

— 

0 

— 

— 

— 

2 

360 

— 

— 

2.52 

9 

Do  . 

810a 

1890 

1080 

1881-1890 

3 

34 

15 

— 

X 

X 

— 

— 

— 

0 

— 

2 

540 

— 

— 

253 

10 

Do  . 

760a 

1890 

1130 

1881-1890 

2 

10 

— 

X 

X 

— 

— 

1 

560 

0 

— 

— 

— 

— 

— 

2.54 

11 

Do  . 

637a 

1890 

1253 

1881-1890 

3 

97 

2 

— 

X 

X 

— 

0 

— 

— 

— 

0 

— 

— 

— 

255 

8 

Do  . 

912o 

1891 

979 

1881-1890 

2 

4 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

250 

4 

Do  . 

1319a 

1887 

568 

1871-1880 

2 

5 

— 

— 

X 

X 

— 

1 

270 

0 

— 

— 

— 

— 

— 

257 

4 

Do  . 

13260 

1880 

554 

1871-1880 

2 

2 

— 

— 

X 

X, 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

258 

4 

Do  . 

1301a 

1886 

585 

1871-1880 

2 

2 

— 

— 

X 

x' 

— 

— 

0 

— 

0 

— 

— 

_ 

— 

— 

2.59 

12 

Do  . 

596a 

1890 

1294 

1881-1890 

3 

35 

22 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

640 

— 

— 

200 

4 

Do  . 

1336a 

1890 

554 

1881-1890 

3 

16 

6 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

270 

_ 

— 

201 

4 

Do  . 

13310 

1890 

559 

1881-1890 

2 

3 

— 

- - 

X 

X 

x: 

— 

0 

— 

0 

_ 

— 

_ 

— 

202 

4 

Do  . 

13240 

1885 

561 

1871-1880 

2 

4 

— 

— 

X 

— 

0 

— 

0 

— 

— 

_ 

_ 

— 

203 

204 

12 

21 

Wigger . 

Do . 

517a 

3336 

1886 

1890 

1369 

2223 

1881-1890 

1881-1890 

3 

4 

7 

206 

8 

213 

33 

X 

N 

X  xi— 

0 

— 

1 

680 

1 

680 

— 

— 

205 

11 

Do . 

622a 

1890 

1268 

1881-1890 

3 

30 

19 

-|X|X| 

— 

— 

— 

0 

— 

1 

630 

— 

— 

Table  C. — Individual  Sequoia  Trees  measured  in  California  in  1911  and  Continued.  305 


U 

<0 

Difference  between 

Readings 

Decades  to  be  added  and  intervals 

d 

aS 

O  » 

B  S 

S  n? 

S  s 

readings. 

to  be  used 

between  them. 

No. 

Place. 

!>.g 

o 

O  X 

if 

o  ^ 

2 

d 

Q 

o 

E 

S  ® 

S 

bc.p 

A. 

B 

p 

D. 

A. 

B. 

D. 

<! 

•< 

Dec 

Int 

Dec 

Int 

Deo 

Int 

Deo 

Int. 

266 

11 

Wisreer . 

525a 

1890 

1265 

1881-1890 

1881-1890 

1881-1890 

1881-1890 

2 

19 

8 

5 

410 

267 

11 

Do . 

606a 

1890 

1284 

2 

1 

268 

12 

Do . 

533a 

1890 

1357 

2 

269 

13 

Do . 

493a 

1890 

1397 

2 

12 

26- 

8 

36 

2 

V 

Y 

700 

270 

14 

Do . 

373a 

1890 

1617 

1881-1890 

1881-1890 

2 

500 

271 

14 

Do . 

376o 

1890 

1514 

2 

V 

Y 

1 

272 

20 

Do . 

2025 

1890 

2092 

1881-1890 

1881-1890 

1881-1890 

2 

V 

273 

10 

Do . 

779a 

1890 

1121 

2 

Y 

Y 

274 

13 

Do . 

446a 

1890 

1444 

2 

98 

— — 

_ 

> 

Fot 

U8 

TO 

275 

13 

Do . 

403a 

1890 

1487 

1881-1890 

2 

28 

9 

8 

2 

Y 

Q 

0 

0 

276 

IS 

Do . 

185 

1890 

’90S 

1881-1890 

2 

Y 

y 

277 

7 

Do . 

1005a 

1890 

1885 

1881-1890 

2 

Y 

X 

Y 

0 

278 

17 

Do . 

11a 

1890 

1879 

1881-1890 

2 

Y 

0 

Q 

279 

9 

Do . 

892a 

1890 

998 

1881-1890 

2 

7 

X 

X 

0 

Q 

0 

280 

8 

Do . 

904a 

1890 

986 

1881-1890 

2 

2 

Y 

Y 

0 

281 

13 

Do . 

449a 

1891 

1442 

1881-1890 

2 

3 

X 

y 

Y 

0 

0 

0 

282 

14 

Do . 

311a 

1890 

1679 

1881-1890 

2 

3 

y 

0 

283 

4 

Do . 

1317a 

1890 

673 

1881-1890 

2 

6 

X 

Y 

0 

Q 

0 

284 

11 

Do . 

606a 

1891 

1285 

1881-1890 

1881-1890 

2 

12 

24 

18 

y 

Y 

1 

2 

640 

236 

16 

Do . 

177a 

1890 

1713 

2 

X 

X 

Y 

0 

570 

286 

22 

Do . 

4795 

1890 

2370 

1881-1890 

2 

X 

0 

0 

287 

288 

11 

Wiggor . 

641a 

1890 

1249 

1881-18S0 

2 

2.3 

_ 

_ 

b 

289 

16 

Do . 

128a 

1890 

1762 

1881-1890 

9 

5 

KXXX- 

Y 

0 

0 

290 

7 

Do . 

i009a 

1890 

881 

1881-1890 

2 

6 

X 

X 

V 

0 

0 

_ 

291 

14 

Do . 

337a 

1890 

1553 

1881-1890 

2 

15 

3 

_ 

_ 

o 

510 

0 

_ 

_ 

_ 

_ 

292 

14 

Do . 

347o 

1890 

1643 

1881-1890 

2 

0 

0 

_ _ 

293 

13 

Do . 

469a 

1890 

1431 

1881-1890 

2 

64 

_ 

Not 

294 

8 

Do . 

012a 

1890 

978 

1881-1890 

2 

9 

X 

X 

- 

0 

_ 

0 

__ 

■ 

__ 

295 

4 

Comstock . 

1320a 

1887 

667 

1871-1880 

4 

23 

1 

8 

X 

X 

0 

0 

___ 

— 

206 

4 

Do  . 

1.337a 

1890 

553 

1881-1890 

2 

1 

X 

X 

_ 

0 

0 

— 

_ 

— 

297 

4 

Do  . 

1327a 

18801- 

553 

1871-1880 

4 

23 

2 

5 

X 

X 

X 

1 

270 

_ 

0 

- 

0 

— 

298 

4 

Do  . 

1330a 

1890 

560 

1881-1890 

2 

4 

X 

X 

0 

0 

_ 

_ 

299 

4 

Do  . 

1333a 

1880 

663 

1871-1880 

2 

1 

X 

X 

— 

0 

__ 

0 

_ 

300 

4 

Do  . 

1310a 

1890 

580 

1881-1890 

2 

18 

_ 

X 

_ 

0 

_ 

_ 

_ _ 

_ 

__ 

301 

4 

Do  . 

1214a 

1890 

676 

1881-1890 

2 

4 

-■ 

_ 

X 

X 

_ 

0 

__ 

0 

— 

_ 

_ 

_ 

302 

6 

Do  . 

1110a 

1890 

771 

1881-1890 

2 

6 

_ 

X 

X 

0 

0 

_ 

_ a 

_ 

_ 

303 

26 

Do  . 

8475 

1905 

2762 

1891-1900 

4 

182 

54 

271 

X 

X 

_ 

5 

450 

— 

_ 

0 

_ 

— 

304 

27 

Converse  W.  F . 

9635 

1902 

2865 

1891-1900 

2 

8 

X 

X 

0 

0 

— 

_ 

— 

— 

— 

305 

17 

Converse  H . 

89a 

1906 

1817 

1891-1900 

3 

70 

87 

_ 

X 

X 

1 

900 

0 

— 

— 

— 

306 

12 

Do  . 

551a 

1900 

1349 

1891-1900 

2 

92 

307 

20 

Do  . 

2435 

1900 

2143 

1891-1900 

2 

2 

— 

X 

X 

_ 

0 

0 

— 

— 

— 

— 

— 

308 

10 

Do  . 

766o 

1892 

1128 

1881-1890 

2 

0 

_ 

_ 

X 

X 

_ 

0 

_ 

0 

— 

— 

— 

— 

— 

309 

16 

Do  . 

1995 

1892 

2091 

1881-1890 

3 

72 

7 

_ 

X 

X 

— 

_ 

_ 

0 

— 

0 

— 

— 

— 

310 

11 

Do  . 

633a 

1892 

1259 

1881-1890 

2 

2 

_ 

X 

X 

— 

0 

_ 

0 

— 

— 

— 

— 

— 

311 

12 

Do  . 

586a 

1904 

1318 

1891-1900 

2 

2 

— 

_ 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

312 

11 

Converse  T.  S . 

614a 

1901 

1287 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

313 

12 

Do  . 

566a 

1904 

1338 

1891-1900 

3 

11 

25 

— 

X 

X 

— 

— 

0 

— 

1 

700 

— 

— 

— 

— 

314 

18 

Do  . 

815 

1904 

1985 

1891-1900 

3 

20 

51 

— 

X 

X 

— 

— 

0 

2 

630 

— 

— 

— 

— 

316 

18 

Do  . 

875 

1904 

1991 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

316 

8 

Do  . 

96Sa 

1904 

936 

1891-1900 

2 

10 

— 

X 

X 

— 

— 

1 

450 

0 

— 

— 

— 

— 

— 

317 

18 

Do  . 

195 

1904 

1923 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

318 

20 

Do  . 

2665 

1904 

2170 

1891-1900 

2 

20 

— 

— 

X 

X 

— 

— 

0 

— 

2 

700 

— 

— 

— 

— 

319 

16 

Do  . 

152a 

1904 

1752 

1891-1900 

2 

12 

— 

— 

X 

X 

— 

— 

0 

1 

800 

— 

— 

— 

— 

320 

21 

Do  . 

3105 

1904 

2214 

1891-1900 

2 

16 

— 

— 

X 

X 

— 

— 

1 

1100 

0 

— 

— 

— 

— 

— 

321 

11 

Do  . 

611a 

1904 

1393 

1891-1900 

2 

13 

— 

— 

X 

X 

— 

— 

0 

— 

1 

630 

— 

— 

— 

— 

322 

11 

Do  . 

653a 

1904 

1251 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

323 

17 

Do  . 

89a 

1904 

1816 

1891-1900 

3 

60 

31 

— 

X 

— 

X 

— 

0 

— 

— 

— 

3 

460 

— 

— 

324 

17 

Do  . 

9Sa 

1904 

1806 

1891-1900 

2 

3 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

325 

12 

Do  . 

511a 

1904 

1393 

1891-1900 

2 

13 

— 

— 

X 

X 

— 

0 

— 

1 

700 

— 

— 

— 

— 

326 

17 

Converse  Mill . 

97a 

1901 

1804 

1891-1900 

2 

3 

— 

— 

X 

X 

— 

0 

— 

0 

610 

— 

— 

— 

— 

327 

17 

Do  . 

37a 

1901 

1864 

1891-1900 

2 

16 

— 

— 

X 

X 

— 

0 

— 

2 

— 

— 

— 

328 

17 

Do  . 

44a 

1901 

1867 

1891-1900 

3 

31 

17 

— 

X 

— 

X 

— 

0 

— 

— 

— 

1 

900 

— 

329 

16 

Do  . 

170a 

1901 

1731 

1891-1900 

3 

27 

21 

— 

X 

X 

— 

0 

— 

0 

— 

2 

5S) 

330 

7 

Do  . 

1035o 

1901 

866 

1891-1900 

2 

12 

— 

— 

X 

X 

— 

— 

1 

400 

— 

— 

— 

— 

— 

331 

9 

Converse  T.  S . 

834a 

1904 

1070 

1891-1900 

3 

34 

11 

— 

X 

X 

— 

1 

520 

— 

— 

0 

— 

332 

19 

Converse  H . 

1836 

1901 

2084 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

0 

— 

0 

600 

— 

333 

11 

Do  . 

650a 

1901 

1251 

1891-1900 

2 

11 

— 

— 

X 

X 

— 

0 

— 

1 

— 

334 

14 

Converse  Mill . 

372a 

1901 

1629 

1891-1900 

2 

6 

— 

— 

X 

X 

— 

0 

— 

0 

1 

1000 

— 

335 

20 

Do  . 

2536 

1901 

2154 

1891-1900 

2 

19 

— 

— 

X 

X 

— 

0 

700 

336 

12 

Do  . 

503a 

1901 

1398 

1891-1900 

2 

13 

— 

— 

X 

X 

1 

0 

337 

10 

Do  . 

744a 

1901 

1157 

1891-1900 

2 

8 

— 

— 

X 

X 

0 

““ 

0 

0 

338 

10 

Do  . 

767a 

1901 

1134 

1891-1900 

2 

3 

— 

— 

X 

X 

0 

339 

12 

Do  . 

6730 

1901 

1327 

1891-1900 

3 

0 

42 

— 

X 

X 

0 

340 

20 

Do  . 

2155 

1901 

2116 

1891-1900 

3 

57 

8 

— 

X 

900 

341 

16 

Do  . 

103o 

1901 

1708 

1891-1900 

2 

14 

— 

X 

X 

1 

342 

12 

Do  . 

5810 

1901 

1320 

1891-1900 

2 

3 

— 

— 

X 

X 

0 

1 

343 

17 

24a 

1892 

1868 

1881-1890 

2 

11 

— 

— 

X 

X 

X 

0 

0 

344 

345 

15 

206a 

1901 

1695 

1891-1900 

3 

21 

2 

X 

0 

10 

772a 

1905 

1133 

1891-1900 

2 

7 

— 

X 

X  ' 

1 

800 

346 

347 

348 

349 

350 

351 

352 

353 

16 

Do  . 

281a 

1903 

1622 

1891-1900 

3 

20 

10 

— 

X  - 

X' 

X 

770 

14 

14 

9 

Do  . 

3G0a 

1901 

1541 

1891-1900 

2 

9 

— 

— 

X 

750 

Do  . 

366a 

1903 

1537 

1891-1900 

2 

16 

25 

— 

X 

X  ■ 

330 

889a 

1903 

1014 

1891-1900 

3 

17 

— 

X 

X  ' 

3 

400 

20 

15 

2726 

1901 

2173 

1891-1900 

3 

121 

33 

X 

X  * 

Do  . 

220a 

1901 

1681 

1891-1900 

2 

10 

— 

X 

X  - 

X- 

1 

Q 

600 

_ 

11 

18 

Do  . 

095a 

1901 

1216 

1891-1900 

2 

15 

— 

X 

1 

Q 

_ 

Converse  Mill . 

446 

1901 

1945 

1891-1900 

3 

228 

1 

"I 

X 

X  - 

- L 

21 


306  Table  C. — Individual  Sequoia  Trees  measured  in  California  in  1911  and  1912 — Continued, 


d 

€8  • 

**■*  M 
®  0 

S  tA 

Last  decade 

measured. 

Difference  between 
readings. 

Readings 
to  be  used. 

Decades  to  be  added  and  intervals 
between  them. 

No. 

o 

o 

Place. 

-  £ 

eS  ^ 

o  c 

o  M 

n 

< 

d 

•< 

Q 

A. 

B. 

c.] 

D. 

A 

B 

C 

. 

D 

<  m 

•y 

< 

Dec. 

Int. 

Deo. 

Int. 

Dec. 

Int. 

Dee. 

Int. 

354 

16 

Converse  Mill . 

141a 

1901 

1 

1760 

1891-1900 

3 

102 

40 

— 

X- 

_ 

0 

355 

20 

Converse  H . 

2806 

1892 

2172 

1881-1890 

3 

31 

36 

— 

X 

X 

X- 

4 

440 

1 

1100 

0 

— 

— 

— 

356 

12 

Do  . 

583a 

1892 

1309 

1881-1890 

2 

8 

— 

— 

X 

X 

1 

700 

0 

— 

— 

— 

— 

— 

357 

20 

Converse  Mill . 

2526 

1901 

2153 

1891-1900 

2 

21 

— 

— 

X 

X 

2 

710 

0 

— 

— 

— 

— 

— 

358 

14 

Do  . 

304a 

1901 

1597 

1891-1900 

2 

1 

— 

— 

X 

X- 

0 

— 

0 

— 

— 

— 

— 

— 

359 

12 

Do  . 

581a 

1901 

1320 

1891-1900 

2 

5 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

360 

11 

Do  . 

698a 

1901 

1203 

1891-1900 

2 

13 

— 

— 

X 

X 

1 

600 

0 

— 

— 

— 

— 

— 

361 

10 

Do  . 

726a 

1901 

1175 

1891-1900 

2 

13 

— 

— 

X 

X 

0 

— 

1 

580 

— 

— 

— 

— 

362 

11 

Do  ....... 

622a 

1901 

1279 

1891-1900 

3 

19 

10 

— 

X- 

X- 

0 

— 

— 

— 

1 

650 

— 

— 

363 

12 

Do  . 

589a 

1901 

1312 

1891-1900 

2 

0 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— • 

— 

364 

15 

Do  . 

201a 

1901 

1700 

1891-1900 

3 

219 

19 

— 

X 

X- 

0 

— 

— 

— 

2 

550 

— 

— 

365 

9 

Converse  No.  6 . 

855a 

1905 

1050 

1891-1900 

2 

0 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

366 

10 

Do  . 

702a 

1903 

1201 

1891-1900 

2 

6 

— 

— 

X 

X- 

0 

— 

0 

— 

— 

— 

— 

— 

367 

12 

Do  . 

511a 

1903 

1392 

1891-1900 

2 

5 

— 

— . 

X 

X 

0 

— 

1 

700 

— 

— 

— 

— 

368 

19 

Do  . 

1856 

1903 

2088 

1891-1900 

3 

35 

10 

— 

X 

X- 

— 

— 

0 

— 

2 

700 

— 

— 

369 

12 

Converse  Camp  No.  1 

534a 

1902 

1368 

1891-1900 

1 

— 

— 

— 

X 

0 

— 

— 

— 

— 

— 

— 

— 

370 

9 

Converse  Mill . 

862a 

1903 

1041 

1891-1900 

2 

1 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

371 

11 

Converse  No.  1 . 

652a 

1904 

1252 

1891-1900 

2 

1 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

372 

13 

Do  . 

462a 

1904 

1442 

1891-1900 

2 

1 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

- - 

373 

15 

Do  . 

225a 

1904 

1679 

1891-1900 

2 

4 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

374 

20 

Do  . 

2576 

1904 

2161 

1891-1900 

2 

3 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

375 

23 

Do  . 

.5096 

1904 

2413 

1891-1900 

2 

9 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

376 

13 

Converse  W.  F . 

460a 

1902 

1442 

1891-1900 

3 

26 

38 

— 

X 

X 

0 

— 

3 

350 

— 

— 

— 

— 

377 

13 

Do  . 

415a 

1902 

1487 

1891-1900 

2 

3 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

378 

14 

Do  . 

347o 

1902 

1555 

1891-1900 

2 

15 

— 

— 

X 

X 

1 

750 

0 

— 

— 

— 

— 

— 

379 

11 

Do  . 

6g0a 

1902 

1212 

1891-1900 

2 

4 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

380 

11 

Do  . 

608a 

1903 

1295 

1891-1900 

2 

46 

— 

— 

X 

0 

— 

— 

— 

— 

— 

— 

— 

381 

19 

Converse  R.  Roy .... 

1566 

1904 

2060 

1891-1900 

3 

66 

9 

— 

X 

— 

X 

0 

— 

— 

— 

0 

— 

— 

— 

382 

20 

Converse  No.  1 . 

2336 

1904 

2137 

1891-1900 

3 

34 

0 

— 

X 

— 

X 

0 

— 

— 

— 

0 

— 

— 

— 

383 

13 

Do  . 

491a 

1904 

1413 

1891-1900 

3 

44 

8 

— 

X 

— 

X 

0 

— 

— 

— 

1 

700 

— 

— 

384 

385 

23 

17 

Do  . 

Do 

5206 

56a 

1004 

1904 

2424 

1848 

1891-1900 

1891-1900 

2 

2 

8 

41 

— 

— 

X 

N 

X 

d 

1 

1200 

0 

— 

— 

— 

— 

— 

386 

22 

Do  . 

4906 

1904 

2394 

1891-1900 

3 

93 

77 

— 

X 

0 

— 

— 

— 

— 

— 

— 

— 

387 

22 

Do  . 

4826 

1904 

2386 

1891-1900 

2 

11 

— 

— 

X 

X 

— 

— 

0 

— 

1 

1200 

— 

— 

— 

— 

388 

24 

Do  . 

6366 

1903 

2539 

1891-1900 

2 

29 

— 

— 

X 

X 

— 

— 

0 

— 

3 

500 

— 

— 

— 

— 

389 

20 

Do  . 

2736 

1903 

2176 

1891-1900 

3 

168 

45 

— 

X 

390 

23 

Converse  W.  F . 

5046 

1894 

2408 

1881-1890 

2 

20 

— 

— 

X 

X 

— 

— 

0 

— 

2 

800 

— 

— 

— 

— 

391 

21 

Do  . 

3766 

1892 

2268 

1881-1890 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

302 

393 

7(14) 

Boule . 

388a 

1904 

1516 

1891-1900 

4 

16 

17 

13 

X 

— 

X 

— 

0 

— 

— 

— 

2 

500 

— 

394 

8(?)11 

Boule . 

687a 

1904 

1217 

1891-1900 

2 

2 

_ 

— 

X 

X 

_ 

0 

_ 

0 

— 

_ 

_ 

_ 

— 

395 

9 

Boule  Camp  No.  4. .  . 

832a 

1904 

1072 

1891-1900 

3 

24 

25 

— 

X 

— 

X 

— 

0 

— 

— 

— 

0 

— 

— 

— 

396 

10 

Converse  Camp  No.  4 

776a 

1904 

1128 

1891-1900 

2 

10 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

397 

19 

Converse  Camp  No.  1 

1366 

1900 

2036 

1891-1900 

2 

10 

— 

— 

X 

X 

— 

— 

0 

— 

1 

1000 

— 

— 

— 

— 

398 

20 

Do 

2116 

1900 

2111 

1891-1900 

3 

65 

11 

— 

X 

— 

X 

— 

0 

— 

- - 

— 

1 

1050 

— 

— 

399 

20 

Do 

2406 

1900 

2140 

1891-1900 

2 

7 

— 

— 

X 

X 

— 

— 

0 

— 

1 

1100 

— 

— 

— 

— 

400 

10 

Converse  W.  F . 

782a 

1902 

1120 

1891-1900 

2 

9 

— 

— 

X 

X 

— 

— 

0 

— 

1 

550 

— 

— 

— 

— 

401 

15 

Do  . 

2.34a 

1902 

1668 

1891-1900 

2 

17 

— 

— 

X 

X 

— 

— 

0 

— 

1 

800 

— 

— 

— 

— 

402 

18(20) 

Boule . 

2586 

1904 

2162 

1891-1900 

3 

95 

88 

— 

— 

X 

X 

— 

— 

— 

0 

— 

1 

1100 

— 

— 

403 

17(19) 

Do . 

1996 

1904 

2103 

1891-1900 

3 

43 

59 

— 

— 

X 

X 

— 

— 

— 

1 

1050 

0 

— 

— 

— 

404 

13 

Converse  No.  4 . 

435a 

1904 

1469 

1891-1900 

2 

9 

— 

— 

X 

X 

— 

— 

1 

700 

0 

— 

— 

— 

— 

— 

405 

11 

Do  . 

089a 

1904 

1215 

1891-1900 

2 

13 

— 

— 

X 

X 

— 

0 

— 

1 

600 

— 

— 

— 

— 

406 

11 

Do  . 

651a 

1904 

1253 

1891-1900 

2 

37 

— 

— 

X 

— 

— 

0 

— 

— 

— 

— 

— 

— 

— 

407 

21 

Converse  Camp  No.  1 

3326 

1900 

2232 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

408 

18 

Do 

786 

1900 

1978 

1891-1900 

2 

3 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

409 

21 

Do 

3156 

1900 

2215 

1891-1900 

2 

4 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

410 

17 

Do 

33a 

1902 

1869 

1891-1900 

4 

51 

31 

25 

— 

— 

X 

X 

— 

— 

— 

— 

0 

— 

0 

— 

411 

23 

Converse  W.  F . 

5896 

1902 

2491 

1891-1900 

3 

120 

15 

— 

X 

— 

X 

0 

— 

— 

— 

1 

1200 

— 

— 

412 

9 

Do  . 

821a 

1902 

1081 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

413 

11 

Do  . 

612a 

1902 

1290 

1891-1900 

2 

4 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

414 

17 

Do  . 

31a 

1902 

1871 

1891-1900 

3 

162 

19 

— 

X 

— 

X 

0 

— 

— 

— 

2 

650 

— 

— 

415 

15 

Do  . 

278a 

1902 

1624 

1891-1900 

2 

8 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

416 

15 

Do  . 

266a 

1902 

1636 

1891-1900 

2 

9 

— 

— 

X 

X 

— 

1 

820 

0 

— 

— 

— 

— 

— 

417 

11 

Do  . 

613a 

1902 

1289 

1891-1900 

2 

4 

— 

— 

X 

X 

— 

0 

— 

0 

— 

— 

— 

— 

— 

418 

12 

Do  . 

588a 

1902 

1314 

1891-1900 

3 

40 

14 

— 

X 

X 

0 

— 

— 

— 

1 

650 

— 

— 

419 

10 

Do  . 

763o 

1902 

1139 

1891-1900 

2 

11 

— 

— 

X 

X 

— 

1 

550 

0 

— 

— 

— 

— 

— 

420 

15 

Do  . 

286a 

1902 

1616 

1891-1900 

2 

31 

— 

— 

X 

X 

— 

3 

400 

0 

— 

— 

— 

— 

— 

421 

22 

Converse  Camp  No.  1 

4136 

1902 

2315 

1891-1900 

2 

48 

— 

— 

X 

X 

4 

450 

0 

— 

— 

— 

— 

— 

422 

25 

Converse  Mill . 

7196 

1902 

2621 

1891-1900 

3 

24 

78 

— 

X 

X 

2 

850 

0 

— 

— 

— 

— 

— 

423 

17 

Converse  W.  F . 

47a 

1902 

1855 

1891-1900 

2 

11 

— 

— 

X 

X 

0 

— 

1 

900 

— 

— 

— 

— 

424 

11 

Do  . 

659a 

1902 

1243 

1891-1900 

2 

5 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

425 

19 

Do  . 

1966 

1902 

2098 

1891-1900 

2 

12 

— 

— 

X 

X 

0 

— 

1 

1050 

— 

— 

— 

426 

13 

Do  . 

432a 

1902 

1470 

1891-1900 

2 

16 

— 

— 

X 

X 

1 

730 

0 

— 

— 

— 

— 

427 

15 

Do  . 

209a 

1902 

1693 

1891-1900 

2 

2 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

428 

11 

Do  . 

6520 

1902 

1250 

1891-1900 

3 

19 

5 

— 

X 

X 

.  2 

420 

0 

— 

— 

— 

— 

— 

429 

11 

Do  . 

605a 

1902 

1297 

1891-1900 

2 

11 

— 

— 

X 

X 

0 

— 

1 

650 

— 

— 

— 

430 

22 

Converse  Mill . 

4386 

1901 

2339 

1891-1900 

2 

3 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

431 

9 

Converse  W.  F . 

875o 

1902 

1027 

1891-1900 

2 

23 

— 

— 

X 

X 

0 

— 

2 

340 

— 

— 

— 

— 

432 

12 

Converse  H . 

551a 

1902 

1351 

1891-1900 

2 

1 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

433 

21 

Converse  W.  F . 

3256 

1902 

2227 

1891-1900 

2 

59 

— 

— 

X 

-  — 

— 

0 

— 

— 

— 

— 

434 

20 

Converse  No.  1 . 

2706 

1903 

2173 

1891-1900 

2 

3 

— 

X 

X 

0 

— 

2 

700 

— 

— 

— 

— 

435 

20 

Converse  W.  F . 

2086 

1902 

2110 

1891-1900 

2 

19 

— 

— 

X 

X 

0 

— 

2 

700 

— 

— 

— 

— 

436 

14 

Converse  No.  1 . 

376a 

1900 

1524 

1891-1900 

2 

2 

— 

— 

X 

X 

0 

— 

0 

— 

— 

— 

— 

— 

437 

9 

Do  . 

S06a 

1900 

1094 

1891-1900 

2 

7 

i  - 

— 

X 

X 

1 

550 

0 

— 

— 

— 

— 

438 

13 

Do  . 

439a 

1900 

1461 

1891-1900 

2 

10 

1  - 

— 

X 

X 

-  0 

— 

1 

700 

— 

— 

— 

— 

430 

14 

Do  . 

357a 

1900 

1543 

1891-1900 

2 

5 

1  - 

— 

X 

X 

-  0 

— 

0 

— 

— 

— 

— 

— 

440 

10 

Do  . 

764a 

1900 

113C 

1891-1900 

2 

6 

X 

X 

-  0 

— 

0 

— 

— 

— 

441 

10 

Do  . 

713a 

1900 

1181 

1801-1900 

2 

10 

j  - 

! 

1  “ 

X 

X 

-  1 

60( 

1  0 

— 

— 

— 

— 

— 

Table  C. — Individual  Sequoia  Trees  measured  in  California  in  1911  and  1912 — Continued.  307 


No. 

Group. 

Place. 

First  year 

of  tree. 

Year  of 

cutting. 

Age  of  tree 

at  cutting. 

a> 

'§■« 
z  1 

-o  i 

ig 
►.1 " 

».i 

Difiference  between 
readings. 

Readings 
to  be  used. 

Decades  to  be  added  and  intervals 
between  them. 

< 

b 

•8 

< 

A&D. 

A. 

B. 

c. 

D. 

A. 

B. 

c. 

D. 

Dec. 

Int. 

Dec. 

Int. 

Dec. 

Int. 

Deo. 

Int 

442 

10 

Converse  No.  1 . 

706a 

1900 

1195 

1891-1900 

2 

9 

X 

X 

1 

600 

0 

443 

14 

Converse  Mill . 

333a 

1901 

1568 

1891-1900 

2 

12 

_ 

_ 

X 

X 

__ 

0 

1 

800 

444 

14 

Do  . 

303a 

1901 

1598 

1891-1900 

2 

11 

_ 

_ 

X 

X 

__ 

1 

800 

0 

445 

16 

Do  . 

102a 

1901 

1709 

1891-1900 

2 

13 

_ 

_ 

X 

X 

- 

_ 

0 

1 

900 

446 

17 

Do  . 

65a 

1901 

1836 

1891-1900 

2 

14 

— 

_ 

X 

X 

_ 

— 

0 

1 

900 

447 

11 

Do  . 

6170 

1896 

1279 

1881-1890 

2 

2 

— 

_ 

X 

X 

_ 

0 

_ 

0 

_ 

448 

17 

Do  . 

70o 

1901 

1831 

1891-1900 

2 

11 

— 

_ 

X 

X 

_ 

1 

900 

0 

__ 

449 

16 

Do  . 

ISOa 

1901 

1751 

1891-1900 

2 

10 

— 

_ 

X 

X 

_ 

_ 

0 

1 

850 

450 

11 

Do  . 

687a 

1901 

1214 

1891-1900 

2 

4 

— 

_ 

X 

X 

_ 

_ 

0 

_ 

0 

_ 

451 

14 

Do  . 

389a 

1901 

1512 

1891-1900 

2 

15 

_ 

_ 

X 

X 

_ 

— 

0 

_ 

1 

800 

452 

17 

Converse  No.  1 . 

265 

1900 

1926 

1891-1900 

3 

72 

62 

_ 

X 

X 

_ 

_ 

0 

1 

900 

_ 

_ 

453 

17 

Do  . 

31a 

1900 

1869 

1891-1900 

2 

18 

— 

_ 

X 

X 

_ 

0 

_ 

2 

600 

_ 

454 

14 

Do  . 

364a 

1900 

1536 

1891-1900 

2 

0 

_ 

_ 

X 

X 

_ 

_ 

0 

_ 

0 

_ 

_ 

_ 

455 

18 

Do  . 

336 

1900 

1933 

1891-1900 

2 

2 

_ 

_ 

X 

X 

_ 

_ 

0 

0 

_ 

_ 

_ 

_ 

456 

9 

Do  . 

804a 

1900 

1096 

1891-1900 

2 

12 

— 

— 

X 

X 

_ 

_ 

2 

350 

0 

_ 

_ 

__ 

_ 

457 

14 

Do  . 

367a 

1900 

1533 

1891-1900 

2 

74 

— 

— 

X 

_ 

_ 

0 

_ 

_ 

_ 

_ 

_ 

___ 

__ 

458 

14 

Do 

3fU/i 

1000 

IKOI^IQOO 

10? 

459 

13 

Do  . 

422a 

1900 

1478 

1891-1900 

3 

22 

11 

_ 

X 

X 

_ 

_ 

0 

_ 

I 

750 

_ 

_ 

460 

13 

Do  . 

427o 

1900 

1473 

1891-1900 

2 

8 

— 

_ 

X 

X 

_ 

0 

_ 

1 

750 

_ 

— 

— 

461 

12 

Converse  Mill . 

500a 

1901 

1341 

1891-1900 

2 

5 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

_ 

_ 

_ 

462 

12 

Do  . 

582o 

1901 

1319 

1891-1900 

2 

0 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

_ 

_ 

_ 

463 

14 

Do  . 

392a 

1901 

1509 

1891-1900 

2 

4 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

_ 

_ 

_ 

464 

15 

Do  . 

204a 

1901 

1699 

1891-1900 

2 

7 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

465 

15 

Do  . 

274a 

1901 

1627 

1891-1900 

2 

10 

— 

— 

X 

X 

— 

— 

0 

— 

1 

800 

— 

— 

— 

— 

466 

14 

Do  . 

336a 

1901 

1565 

1891-1900 

2 

5 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

467 

12 

Do  . 

528a 

1901 

1373 

1891-1900 

2 

3 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

468 

13 

Do  . 

418a 

1901 

1483 

1891-1900 

2 

5 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

469 

16 

Do  . 

182a 

1901 

1719 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

470 

12 

Do  . 

505o 

1901 

1396 

1891-1900 

2 

2 

— 

— 

X 

X 

— 

— 

0 

— 

0 

— 

— 

— 

— 

— 

Note  on  Location  of  Placet. — Aside  from  Millwood  and  Hume,  the  localities  here  mentioned  are  merely  local  names  of  mills,  etc.  They  may  be 
grouped  as  follows  :  (A)  Millwood  east  of  Sanger  ;  (B)  Parts  of  Converse  Basin  north  of  Millwood,  vis.  Boule,  Rob  Roy,  T.  S.  =  Three  Sisters,  H  == 
Hoist,  W.  F.=  World’s  Fair  Tree  district;  (C)  Indian  Basin  between  Converse  Basin  and  Hume;  (D)  Hume;  (E)  Enterprise,  Coburn,  Frasier,  and 
Mountain  Home  east  of  Portersville  ;  (F)  Dillonwood  north  of  (E)  ;  (G)  Comstock  and  Wigger,  southeast  of  Millwood;  (H)  Eldorado  in  Calaveras 
County. 


Table  D. — Summary  of  Seqtioia  Trees,  by  Groups. 


Group. 

Average 

age. 

No.  of 
trees. 

No.  of  meas¬ 
urements. 

No.  of  trees 
having 
more  than 
one 

measure¬ 

ment. 

Diff.  of  Ist  and 
2d  readings — 
years. 

Decades  added. 

Used. 

Not 

used. 

Total. 

Aver¬ 

age. 

No.  of 
cases. 

Total  No. 
of  decades. 

1 

250 

6 

7 

0 

1 

3 

3 

0 

0 

2 

350 

7 

8 

0 

1 

2 

2 

0 

0 

3 

450 

11 

15 

0 

4 

11 

3 

0 

0 

4 

550 

37 

63 

9 

26 

286 

11 

9 

9 

5 

650 

16 

21 

3 

6 

64 

11 

0 

9 

6 

750 

8 

10 

1 

3 

22 

7 

5 

5 

7 

850 

11 

17 

2 

7 

72 

10 

5 

5 

8 

950 

19 

26 

2 

8 

76 

9 

13 

13 

9 

1,050 

22 

42 

6 

15 

195 

13 

14 

19 

10 

1,150 

20 

42 

2 

20 

188 

9 

13 

13 

11 

1,250 

38 

75 

8 

37 

589 

16 

18 

22 

12 

1,350 

32 

59 

10 

27 

332 

12 

16 

19 

13 

1,450 

28 

49 

7 

22 

353 

16 

22 

35 

14 

1,550 

28 

51 

9 

26 

488 

19 

14 

21 

15 

1,650 

29 

47 

12 

19 

611 

32 

21 

36 

16 

1,750 

20 

33 

4 

IS 

335 

22 

15 

29 

17 

1,850 

24 

47 

12 

22 

652 

30 

15 

24 

18 

1,950 

16 

30 

5 

13 

459 

35 

8 

14 

19 

2,050 

15 

25 

7 

10 

384 

38 

11 

23 

20 

2,150 

26 

49 

15 

25 

946 

38 

18 

34 

21 

2,250 

9 

17 

1 

8 

139 

17 

4 

11 

22 

2,350 

12 

24 

10 

11 

441 

40 

9 

24 

23 

2,450 

7 

11 

1 

4 

157 

39 

6 

14 

24 

2,550 

1 

2 

0 

1 

29 

29 

1 

3 

25 

2,650 

2 

4 

1 

2 

65 

33 

2 

6 

26 

2,750 

3 

6 

2 

2 

197 

99 

2 

7 

27 

2,850 

1 

2 

0 

1 

8 

8 

0 

0 

28 

29 

3,050 

1 

1 

0 

0 

30 

3,150 

1 

1 

3 

1 

480 

480 

0 

0 

31 

3,250 

1 

2 

2 

1 

68 

68 

1 

3 

Total . 

451 

785 

134 

338 

7,652 

22.6 

252 

404 

308 


Table  E. — Combined  Corrective  Factors  for  Age  and  for  Longevity,  Sequoia  washingtoniana. 


Decade 
of  life 
of  tree. 


1 

2 

3 

4 

5 

6 

7 

8 
9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 
21 
22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

53 

54 
65 

56 

57 

58 

59 

60 
61 
62 

63 

64 

65 

66 

67 

68 

69 

70 

71 

72 

73 

74 

75 

76 

77 

78 

79 

80 


Estimated 
value  of 
smoothed 


Combined  corrective  factor  for  age  and  longevity. 


growth 
shown  in 
figs.  35 
and  36. 

Groups 

1-9* 

Group 

10 

Group 

11 

Group 

12 

Group 

13 

Group 

14 

Group 

15 

Group 

16 

Group 

17 

Group 

18 

Group 

19 

Group 

20 

Group 

21 

Group 

22 

Group 

23 

Group 

24 

Group 

25 

Groups 

26-ai 

27.5 

22.5 

22.6 

22.9 

23.3 

23.6 

24.2 

24.7 

25.2 

25.7 

26.1 

26.7 

27.2 

27.7 

28.2 

28.6 

29.0 

29.4 

29.8 

26.3 

23.6 

23.7 

24.1 

24.4 

24.8 

25.4 

25.9 

26.4 

26.9 

27.4 

28.0 

28.5 

29.0 

29.6 

30.0 

30.4 

30.9 

31.3 

25.2 

24.6 

24.8 

25.1 

25.5 

25.8 

26.4 

26.9 

27.5 

28.1 

28.5 

29.2 

29.7 

30.3 

30.9 

31.3 

31.7 

31.9 

32.6 

24.6 

25.2 

25.4 

25.7 

26.1 

26.4 

27.1 

27.6 

28.2 

28.7 

29.2 

29.9 

30.4 

31.0 

31.6 

32.0 

32.5 

32.9 

33.4 

24.0 

25.8 

26.0 

26.3 

26.7 

27.1 

27.7 

28.3 

28.9 

29.4 

29.9 

30.6 

31.1 

31.7 

32.4 

32.8 

33.2 

33.7 

34.2 

23.5 

26.4 

26.6 

26.9 

27.3 

27.7 

28.4 

28.9 

29.6 

30.1 

30.6 

31.3 

31.8 

32.5 

33.1 

33.6 

34.0 

34.5 

35.0 

23.0 

26.9 

27.0 

27.4 

27.9 

28.2 

28.9 

29.5 

30.1 

30.7 

31.2 

31.9 

32.4 

33.1 

33.8 

34.2 

34.7 

35.2 

35.7 

22.6 

27.4 

27.5 

27.9 

28.4 

28.8 

29.4 

30.0 

30.7 

31.2 

31.8 

32.5 

33.0 

33.7 

34.4 

34.8 

35.3 

35.8 

36.3 

22.2 

27.9 

28.0 

28.4 

28.9 

29.3 

30.0 

30.6 

31.2 

31.8 

32.3 

33.0 

33.7 

34.3 

35.0 

35.4 

35.9 

36.5 

37.0 

21.9 

28.3 

28.4 

28.8 

29.3 

29.7 

30.4 

31.0 

31.7 

32.3 

32.8 

33.6 

34.2 

34.8 

35.5 

36.0 

36.4 

37.0 

37.5 

21.7 

28.6 

28.7 

29.1 

29.6 

30.0 

30.8 

31.4 

32.0 

32.6 

33.2 

33.9 

34.5 

35.2 

35.9 

36.4 

36.8 

37.4 

37.9 

21.4 

28.9 

29.0 

29.4 

29.9 

30.3 

31.1 

31.7 

32.4 

33.0 

33.6 

34.3 

34.9 

35.6 

36.3 

36.7 

37.2 

37.8 

38.3 

21.2 

29.2 

29.3 

29.7 

30.2 

30.6 

31.4 

32.0 

32.7 

33.3 

33.9 

34.6 

35.2 

35.9 

36.6 

37.1 

37.6 

38.2 

38.7 

21.0 

29.5 

29.6 

30.0 

30.6 

31.0 

31.7 

32.3 

33.1 

33.6 

34.2 

35.0 

35.6 

36.3 

37.0 

37.5 

38.0 

38.6 

39.1 

20.8 

29.8 

29.9 

30.3 

30.9 

31.3 

32.0 

32.6 

33.4 

34.0 

34.6 

35.3 

36.0 

36.7 

37.4 

37.9 

38.4 

39.0 

39.6 

20.6 

30.1 

30.2 

30.6 

31.2 

31.6 

32.3 

33.0 

33.7 

34.3 

34.9 

35.7 

36.3 

37.0 

37.7 

38.2 

38.8 

39.4 

39.9 

20.4 

30.4 

30.6 

30.9 

31.5 

31.9 

32.7 

33.3 

34.1 

34.7 

35.3 

36.0 

36.7 

37.4 

38.1 

38.6 

39.2 

39.8 

40.3 

20.2 

30.7 

30.9 

31.2 

31.8 

32.2 

33.0 

33.6 

34.4 

35.0 

35.6 

36.4 

37.0 

37.8 

38.5 

39.0 

39.6 

40.2 

40.7 

20.0 

31.0 

31.2 

31.5 

32.1 

32.5 

33.3 

33.9 

34.7 

35.3 

36.0 

36.8 

37.4 

38.2 

38.9 

39.4 

39.9 

40.6 

41.1 

19.8 

31.3 

31.5 

31.8 

32.4 

32.9 

33.6 

34.3 

35.1 

35.7 

36.3 

37.1 

37.8 

38.6 

39.2 

39.8 

40.3 

40.9 

41.6 

19.6 

31.6 

31.8 

32.2 

32.7 

33.2 

34.0 

34.6 

35.4 

36.0 

36.7 

37.4 

38.1 

38.9 

39.6 

40.2 

40.7 

41.3 

41.8 

19.4 

31.9 

32.1 

32.5 

33.0 

33.5 

34.3 

34.0 

35.7 

36.4 

37.0 

37.8 

38.5 

39.2 

40.0 

40.5 

41.1 

41.7 

42.3 

19.2 

32.3 

32.5 

32.9 

33.5 

33.9 

34.7 

35.4 

36.2 

36.8 

37.5 

38.3 

39.0 

39.7 

40.5 

41.0 

41.6 

42.3 

42.8 

19.0 

32.6 

32.8 

33.2 

33.8 

34.2 

35.0 

35.7 

36.5 

37.2 

37.8 

38.6 

39.3 

40.2 

40.8 

41.5 

42.0 

42.7 

43.2 

18.8 

33.0 

33.2 

33.6 

34.2 

34.6 

35.5 

36.2 

37.0 

37.6 

38.3 

39.1 

39.8 

40.6 

41.4 

41.9 

42.5 

43.2 

43.8 

18.6 

33.3 

33.5 

33.9 

34.5 

34.9 

35.8 

36.5 

37.3 

38.0 

38.6 

39.5 

40.2 

41.0 

41.7 

42.4 

42.9 

43.6 

44.1 

18.4 

33.7 

33.9 

34.3 

34.9 

35.3 

36.2 

36.9 

37.8 

38.4 

39.1 

40.0 

40.7 

41.5 

42.2 

42.8 

43.4 

43.9 

44.6 

18.2 

34.1 

34.3 

34.7 

35.3 

35.8 

36.6 

37.3 

38.2 

38.9 

39.6 

40.4 

41.1 

42.0 

42.3 

43.3 

43.9 

44.5 

45.2 

18.0 

34.4 

34.6 

35.0 

35.6 

36.1 

37.0 

37.7 

38.5 

39.2 

39.9 

40.8 

41.5 

42.4 

43.2 

43.7 

44.3 

45.0 

45.6 

17.8 

34.8 

35.0 

35.4 

36.0 

36.5 

37.4 

38.1 

39.0 

39.7 

40.3 

41.2 

42.0 

42.8 

43.7 

44.2 

44.8 

45.5 

46.1 

17.6 

35.2 

35.4 

35.9 

36.4 

36.9 

37.8 

38.6 

39.4 

40.2 

40.8 

41.7 

42.4 

43.3 

44.2 

44.7 

45.3 

46.0 

46.6 

17.4 

35.6 

35.8 

36.3 

36.8 

37.3 

38.2 

39.0 

39.9 

40.6 

41.3 

42.7 

42.9 

43.8 

44.7 

45.2 

45.8 

46.6 

47.2 

17.2 

36.0 

36.2 

36.7 

37.2 

37.8 

38.7 

39.4 

40.3 

41.1 

41.8 

42.2 

43.4 

44.3 

45.2 

45.8 

46.4 

47.1 

47.7 

17.0 

36.5 

36.7 

37.2 

37.7 

38.3 

39.2 

40.0 

40.9 

41.6 

42,4 

43.3 

44.0 

44.9 

45.8 

46.4 

47.0 

47.7 

48.4 

16.8 

36.9 

37.1 

37.6 

38.2 

38.7 

39.7 

40.5 

41.3 

42.1 

42.8 

43.7 

44.5 

45.5 

46.3 

47.0 

47.5 

48.3 

48.9 

16.6 

37.4 

37.6 

38.1 

38.7 

39.2 

40.2 

41.0 

41.8 

42.6 

43.4 

44.3 

45.1 

46.0 

46.9 

47.6 

48.2 

48.8 

49.6 

16.45 

37.7 

37.9 

38.4 

39.0 

39.6 

40.5 

41.3 

42.2 

43.0 

43.7 

44.7 

45.5 

46.4 

47.3 

48.0 

48.6 

49.3 

49.9 

16.3 

38.0 

38.2 

38.7 

39.3 

39.9 

40.8 

41.7 

42.6 

43.3 

44.1 

45.0 

45.9 

46.8 

47.7 

48.4 

49.0 

49.7 

50.3 

16.15 

38.4 

38.6 

39.1 

39.8 

40.3 

41.2 

42.1 

43.0 

43.8 

44.6 

45.5 

46.3 

47.2 

48.2 

48.9 

49.4 

60.2 

50.8 

16.0 

38.8 

38.9 

39.4 

40.1 

40.6 

41.6 

42.4 

43.4 

44.1 

45.0 

45.8 

46.6 

47.6 

48.5 

49.3 

49.9 

50.6 

51.3 

15.8 

39.2 

39.4 

39.9 

40.6 

41.1 

42.1 

42.9 

43.9 

44.7 

45.5 

46.4 

47.2 

48.2 

49.1 

49.8 

50.5 

51.2 

51.8 

15.6 

39.7 

39.9 

40.4 

41.1 

41.6 

42.7 

43.5 

44.5 

45.3 

46.0 

47.1 

47.9 

48.8 

49.8 

50.5 

51.1 

51.9 

52.5 

15.4 

40.2 

40.4 

40.9 

41.6 

42.1 

43.2 

44.0 

45.0 

45.8 

46.6 

47.6 

48.5 

49.5 

50.3 

51.0 

51.7 

62.5 

63.2 

15.2 

40.8 

41.0 

41.5 

42.2 

42.8 

43.8 

44.7 

45.7 

46.5 

47.3 

48.3 

49.2 

50.2 

51.2 

51.8 

52.5 

53.4 

54.0 

15.0 

41.3 

41.5 

42.0 

42.7 

43.3 

44.4 

45.2 

46.3 

47.1 

48.0 

49.0 

49.8 

50.9 

51.8 

52.5 

53.2 

54.0 

54.7 

14.85 

41.7 

41.9 

42.4 

43.1 

43.6 

44.8 

45.7 

46.7 

47.5 

48.4 

49.5 

50.3 

51.3 

52.3 

53.0 

53.7 

54.5 

55.2 

14.7 

42.2 

42.4 

42.9 

43.6 

44.2 

45.3 

46.2 

47.2 

48.0 

49.0 

50.0 

51.0 

52.0 

53.0 

63.5 

54.3 

55.1 

55.9 

14.55 

42.6 

42.8 

43.3 

44.0 

44.7 

45.8 

46.6 

47.7 

48.6 

49.4 

50.5 

51.5 

52.5 

53.5 

54.1 

54.9 

55.7 

56.5 

14.40 

43.0 

43.2 

43.7 

44.5 

45.1 

46.2 

47.1 

48.2 

49.0 

49.9 

51.0 

51.9 

53.0 

54.0 

54.7 

55.4 

56.2 

67.0 

14.25 

43.5 

43.7 

44.2 

45.0 

45.6 

46.8 

47.7 

48.7 

49.6 

50.5 

51.6 

52.5 

53.5 

54.5 

55.3 

56.0 

56.9 

57.6 

14.05 

44.2 

44.4 

45.0 

45.7 

46.3 

47.5 

48.4 

49.5 

50.4 

51.2 

52.4 

53.2 

54.3 

55.4 

56.1 

56.8 

57.6 

58.3 

13.90 

44.6 

44.8 

45.4 

46.1 

46.8 

47.9 

48.9 

50.0 

50.8 

51.7 

52.8 

53.8 

54.9 

55.9 

56.7 

57.5 

58.4 

59.0 

13.70 

45.2 

45.4 

46.0 

46.7 

47.4 

48.5 

49.5 

50.6 

51.5 

52.4 

53.5 

54.5 

55.6 

56.6 

57.4 

58.2 

59.1 

59.7 

13.55 

45.7 

46.0 

46.5 

47.2 

47.9 

49.1 

50.0 

51.2 

52.0 

53.0 

54.2 

55.1 

56.2 

57.3 

58.1 

58.8 

59.7 

60.5 

13.35 

46.4 

46.7 

47.2 

47.9 

48.7 

49.9 

50.8 

52.0 

52.9 

53.8 

55.0 

56.0 

57.1 

58.1 

59.0 

59.7 

60.6 

61.3 

13.2 

46.9 

47.2 

47.8 

48.6 

49.3 

50.4 

51.4 

52.6 

53.5 

54.4 

55.6 

56.6 

57.7 

58.8 

59.7 

60.4 

61.4 

62.1 

13.05 

47.5 

47.8 

48.4 

49.2 

49.9 

51.1 

52.0 

53.2 

54.2 

55.2 

56.3 

57.3 

58.5 

59.6 

60.4 

61.2 

62.1 

62.8 

12.85 

48.2 

48.6 

49.2 

50.0 

50.8 

52.0 

52.9 

54.2 

55.1 

56.0 

57.1 

58.2 

59.3 

60.5 

61.3 

62.0 

63.0 

63.7 

12.7 

48.8 

49.1 

49.7 

50.5 

51.3 

52.5 

53.5 

54.8 

55.7 

56.7 

57.9 

59.0 

60.0 

61.2 

62.1 

62.9 

63.9 

64.6 

12.55 

49.4 

49.7 

50.3 

51.2 

51.9 

53.1 

54.1 

55.3 

56.3 

57.3 

58.5 

59.6 

60.8 

61.9 

02.8 

63.6 

04.6 

65.4 

12.35 

50.2 

50.5 

51.2 

52.0 

52.7 

53.9 

55.0 

56.2 

57.2 

58.2 

59.5 

60.5 

61.7 

62.9 

63.8 

64.6 

65.6 

66.4 

12.2 

50.8 

51.1 

.51.8 

52.6 

53.4 

54.6 

55.7 

57.0 

58.0 

59.0 

60.2 

61.3 

62.5 

63.7 

64.5 

65.4 

66.5 

67.3 

12.05 

51.5 

51.8 

52.5 

53.3 

54.1 

55.3 

56.4 

57.7 

58.7 

59.8 

61.0 

62.1 

63.4 

64.6 

65.5 

66.3 

67.4 

68.2 

11.85 

52.3 

52.6 

53.3 

54.1 

54.9 

56.2 

57.3 

58.6 

59.6 

60.7 

62.0 

63.1 

64.4 

65.6 

66.5 

67.3 

68.5 

69.3 

11.7 

53.0 

53.3 

54.0 

54.8 

55.6 

57.0 

58.1 

59.4 

60.4 

61.5 

62.8 

6-1.0 

65.3 

66.5 

67.4 

68.3 

69.3 

70.2 

11.55 

53.7 

54.0 

54.7 

55.6 

56.4 

57.7 

58.8 

60.1 

61.2 

62.2 

63.7 

64.8 

66.1 

67.3 

68.2 

69.1 

70.2 

71.1 

11.40 

54.4 

54.7 

55.4 

56.3 

57.1 

58.5 

59.5 

61.0 

62.0 

63.1 

64.5 

65.5 

66.9 

68.2 

69.1 

70.0 

71.1 

72.0 

11.25 

55.1 

55.4 

56.1 

57.0 

57.9 

59.2 

60.4 

61.7 

62.8 

64.0 

65.4 

66.5 

67.8 

69.1 

70.1 

71.0 

72.0 

73.0 

11.10 

55.8 

56.1 

56.8 

57.7 

58.6 

60.0 

61.2 

62.6 

63.7 

64.7 

66.2 

67.4 

68.6 

70.0 

71.0 

72.0 

73.0 

74.0 

10.95 

56.6 

57.0 

57.7 

58.6 

59.5 

61.0 

62.0 

63.5 

64.7 

65.7 

67.2 

68.4 

69.7 

71.1 

72.0 

73.0 

74.0 

75.0 

10.80 

57.3 

57.6 

58.4 

59.3 

60.2 

61.6 

62.8 

64.2 

65.4 

66.5 

68.0 

69.3 

70.5 

71.9 

72.8 

73.9 

76.0 

75.9 

10.7 

57.9 

58.2 

59.0 

59.9 

60.8 

62.2 

63.4 

64.9 

66.0 

67.1 

68.6 

70.0 

71.3 

72.7 

73.6 

74.7 

75.9 

76.7 

10.6 

58.5 

.58.8 

59.6 

60.5 

61.4 

62.9 

64.1 

65.6 

66.7 

67.9 

69.4 

70.6 

72.0 

73.5 

74.4 

75.5 

76.7 

77.5 

10.5 

59.1 

59.4 

60.2 

61.1 

62.1 

63.5 

64.8 

66.2 

67.4 

68.5 

70.0 

71.3 

72.7 

74.1 

75.1 

76.2 

77.4 

78.2 

10.4 

59.7 

60.0 

60.8 

61.6 

62.7 

64.2 

65.4 

66.9 

68.0 

69.3 

70.7 

72.0 

73.5 

74.9 

75.9 

77.0 

78.1 

79.0 

10.3 

60.3 

60.6 

61.4 

62.4 

63.4 

64.8 

66.1 

67.5 

68.8 

70.0 

71.5 

72.8 

74.2 

75.7 

76.6 

77.8 

79.0 

79.9 

10.2 

60.9 

61.2 

62.0 

63.0 

M.0 

65.5 

66.7 

68.2 

69.5 

70.6 

72.1 

73.5 

75.0 

76.4 

774 

78.5 

79.8 

80.6 

10.1 

61.5 

61.8 

62.6 

63.7 

64.8 

66.1 

67.4 

68.8 

70.1 

71.4 

72.9 

74.1 

75.6 

77.1 

78.2 

79.2 

80.5 

81.4 

10.0 

62.1 

62.4 

63.2 

64.3 

65.5 

66.8 

68.0 

69.6 

70.9 

72.0 

73.6 

75.0 

76.4 

77.9 

79.0 

80.0 

81.2 

82.2 

9.9 

62.7 

63.0 

63.8 

64.9 

66.2 

67.4 

68.6 

70.2 

71.5 

72.7 

74.3 

75.6 

77.1 

78.7 

79.6 

80.8 

82.0 

83.0 

*  This  column,  showing  the  corrective  factor  for  groups  1-9,  is  the  unaltered  factor  for  age  alone,  no  correction  for  longevity  having  seemed  necessary  in  these  groups. 


Table  E.  Combined  Corrective  Factors  for  Age  and  for  Lo7igevity,  Sequoia  waskingtoniana — Cont’d.  309 


Estimated 


Decade 
of  life 
of  tree. 

value  of 
smoothed 
curve  of 

Combined  corrective  faptor  for  age  and  longevity. 

growth 
shown  in 
6gs.  35 
and  36. 

Groups 

1-9 

Group 

10 

Group 

11 

Group 

12 

Group 

13 

Group 

14 

Group 

15 

Group 

16 

Group 

17 

Group 

18 

Group 

19 

Group 

20 

Group 

21 

Group 

22 

Group 

23 

Group 

24 

Group 

25 

Groups 

26-31 

81 

9.85 

63.0 

63.3 

64.3 

65.3 

66.4 

67.8 

69.0 

70.5 

71.8 

73.1 

74.6 

76.0 

77.5 

79.1 

80.6 

81.2 

82.5 

83.5 

82 

9.8 

63.3 

63.6 

64.6 

65.6 

66.7 

68.1 

69.4 

70.9 

72.2 

73.5 

75.0 

76.4 

77.9 

79.5 

81.0 

81.6 

82.9 

83.9 

83 

9.75 

63.7 

64.0 

65.0 

66.0 

67.0 

68.5 

69.8 

71.3 

72.6 

73.9 

75.4 

76.8 

78.3 

80.0 

81.4 

82.0 

83.4 

84.4 

84 

9.7 

64.0 

64.3 

65.3 

66.3 

67.3 

68.9 

70.2 

71.7 

73.0 

74.3 

75.8 

77.2 

78.7 

80.4 

81.8 

82.4 

83.8 

84.8 

85 

9.65 

64.3 

64.6 

65.6 

66.6 

67.6 

69.2 

70.6 

72.1 

73.4 

74.7 

76.2 

77.6 

79.1 

80.9 

82.2 

82.8 

84.3 

85.3 

86 

9.6 

64.7 

65.0 

66.0 

67.0 

68.0 

69.6 

71.0 

72.6 

73.8 

75.1 

76.6 

78.0 

79.5 

81.3 

82.6 

83.2 

84.7 

85.7 

87 

9.55 

65.0 

65.3 

66.3 

67.4 

68.3 

69.9 

71.4 

72.9 

74.2 

75.5 

77.0 

78.4 

79.9 

81.7 

83.0 

83.6 

85.1 

86.1 

88 

9.5 

65.3 

65.6 

66.6 

67.7 

68.6 

70.3 

71.7 

73.2 

74.5 

75.8 

77.4 

78.8 

80.3 

82.1 

83.4 

84.0 

85.6 

86.6 

89 

9.45 

65.7 

66.0 

67.0 

68.1 

69.0 

70.7 

72.0 

73.6 

74.8 

76.2 

77.8 

79.2 

80.7 

82.5 

83.8 

84.4 

85.9 

86.9 

90 

9.4 

66.0 

66.3 

67.3 

68.4 

69.4 

71.0 

72.3 

73.9 

75.1 

76.6 

78.2 

79.6 

81.1 

82.9 

84.2 

84.8 

86.4 

87.4 

91 

9.36 

66.3 

66.6 

67.7 

68.7 

69.7 

71.3 

72.6 

74.2 

75.4 

77.0 

78.6 

79.9 

81.4 

83.3 

84.6 

85.2 

86.8 

87.8 

92 

9.32 

66.6 

66.9 

67.9 

69.0 

70.0 

71.6 

72.9 

74.5 

75.7 

77.4 

79.0 

80.3 

81.8 

83.7 

85.0 

85.6 

87.1 

88.1 

93 

9.28 

66.9 

67.2 

68.2 

69.3 

70.3 

71.9 

73.2 

74.8 

76.0 

77.8 

79.4 

80.6 

82.1 

84.1 

85.4 

86.0 

87.5 

88.5 

94 

9.24 

67.2 

67.5 

68.5 

69.6 

70.6 

72.2 

73.5 

75.1 

76.3 

78.2 

79.8 

81.0 

82.5 

84.5 

85.8 

86.4 

87.8 

88.8 

95 

9.2 

67.4 

67.7 

68.7 

69.8 

70.9 

72.5 

73.8 

75.4 

76.6 

78.5 

80.2 

81.3 

82.8 

84.9 

86.2 

86.8 

88.2 

89.2 

90 

9.16 

67.7 

68.0 

69.0 

70.1 

71.2 

72.8 

74.1 

75.7 

76.9 

78.8 

80.6 

81.7 

83.2 

85.3 

86.6 

87.2 

88.6 

89.6 

97 

9.12 

68.0 

68.3 

69.3 

70.4 

71.5 

73.1 

74.4 

76.0 

77.3 

79.1 

80.9 

82.0 

83.5 

85.7 

87.0 

87.6 

89.0 

90.0 

98 

9.08 

68.3 

68.6 

69.6 

70.7 

71.8 

73.4 

74.7 

76.3 

77.7 

79.4 

81.2 

82.4 

83.9 

86.1 

87.4 

88.0 

89.4 

90.4 

99 

9.04 

68.6 

68.9 

69.9 

71.0 

72.1 

73.7 

75.0 

76.6 

78.1 

79.7 

81.5 

82.7 

84.2 

86.5 

87.8 

88.2 

89.8 

90.8 

100 

9.0 

68.9 

69.2 

70.2 

71.3 

72.4 

74.1 

75.4 

77.0 

78.5 

80.0 

81.8 

83.1 

84.6 

86.9 

88.2 

88.8 

90.2 

91.2 

101 

8.96 

69.2 

69.5 

70.5 

71.6 

72.7 

74.6 

75.7 

77.4 

78.9 

80.4 

82.2 

83.5 

85.0 

87.3 

88.6 

89.2 

90.6 

91.6 

102 

8.92 

69.6 

69.9 

70.9 

72.0 

73.1 

74.9 

76.0 

77.8 

79.3 

808 

82.6 

83.9 

85.5 

87.7 

89.0 

89.6 

91.1 

92.1 

103 

8.88 

69.9 

70.2 

71.2 

72.4 

73.5 

75.3 

76.4 

78.2 

79.7 

81.2 

83.0 

84.3 

85.9 

88.1 

89.4 

90.0 

91.5 

92.5 

104 

8.84 

70.3 

70.6 

71.6 

72.8 

73.9 

75.6 

76.8 

78.6 

80.1 

81.6 

83.4 

84.7 

86.4 

88.5 

89.8 

90.4 

92.0 

93.0 

105 

8.8 

70.6 

70.9 

72.0 

73.2 

74.2 

76.0 

77.2 

79.0 

80.5 

82.0 

83.8 

85.1 

86.8 

88.9 

90.2 

90.8 

92.4 

93.4 

106 

8.76 

71.0 

71.3 

72.4 

73.6 

74.6 

76.4 

77.6 

79.4 

80.9 

82.4 

84.2 

85.5 

87.3 

89.3 

90.6 

91.1 

92.9 

93.9 

107 

8.72 

71.3 

71.7 

72.7 

73.9 

74.9 

76.7 

78.0 

79.8 

81.3 

82.8 

84.6 

85.9 

87.7 

89.7 

91.0 

91.4 

93.3 

94.3 

108 

8.68 

71.6 

72.0 

73.0 

74.2 

75.2 

77.0 

78.4 

80.2 

81.7 

83.2 

85.0 

86.3 

88.2 

90.1 

91.4 

91.7 

93.8 

94.8 

109 

8.64 

71.9 

72.3 

73.4 

74.6 

75.5 

77.3 

78.8 

80.6 

82.1 

83.5 

85.3 

86.7 

88.6 

90.5 

91.8 

92.0 

94.2 

95.2 

110 

8.6 

72.3 

72.7 

73.7 

74.9 

75.9 

77.8 

79.1 

81.0 

82.5 

83.9 

85.7 

87.1 

89.1 

90.9 

92.2 

92.3 

94.7 

95.7 

111 

8.57 

72.6 

73.0 

74.0 

75.2 

76.2 

78.1 

79.4 

81.3 

82.8 

84.2 

86.0 

87.4 

89.5 

91.2 

92.5 

92.7 

95.0 

96.0 

112 

8.54 

72.8 

73.2 

74.2 

75.5 

76.5 

78.4 

79.7 

81.6 

83.1 

84.5 

86.3 

87.7 

89.8 

91.5 

92.9 

93.1 

95.3 

96.3 

113 

8.51 

73.1 

73.5 

74.5 

75.8 

76.8 

78.7 

80.0 

81.9 

83.4 

84.8 

86.6 

88.0 

90.1 

91.8 

93.2 

93.5 

95.6 

96.6 

114 

8.49 

73.3 

73.7 

74.7 

76.0 

77.1 

79.0 

80.3 

82.2 

83.7 

85.1 

86.9 

88.3 

90.4 

92.1 

93.6 

93.9 

95.9 

96.9 

115 

8.46 

73.5 

73.9 

74.9 

76.2 

77.4 

79.2 

80.6 

82.5 

83.9 

85.4 

87.2 

88.6 

90.7 

92.4 

93.9 

94.3 

96.2 

97.2 

116 

8.43 

73.8 

74.2 

75.2 

76.5 

77.7 

79.5 

80.9 

82.8 

84.2 

85.7 

87.5 

88.9 

91.0 

92.7 

94.3 

94.7 

96.5 

97.5 

117 

8.4 

74.0 

74.4 

75.5 

76.7 

77.9 

79.7 

81.2 

83.1 

84.4 

85.9 

87.8 

89.2 

91.3 

93.0 

94.6 

95.1 

96.8 

97.8 

118 

8.37 

74.2 

74.6 

75.7 

76.9 

78.1 

80.0 

81.4 

83.3 

84.6 

86.1 

88.1 

89.5 

91.6 

93.3 

95.0 

95.5 

97.1 

98.1 

119 

8.34 

74.4 

74.8 

75.9 

77.1 

78.3 

80.2 

81.6 

83.5 

84.8 

86.3 

88.3 

89.8 

91.9 

93.6 

95.3 

95.9 

97.4 

98.4 

120 

8.31 

74.7 

75.1 

76.2 

77.4 

78.5 

80.4 

81.8 

83.7 

85.1 

86.6 

88.6 

90.1 

92.2 

93.9 

95.6 

96.3 

97.7 

98.8 

121 

8.28 

74.9 

75.3 

76.4 

77.7 

78.7 

80.7 

82.1 

84.0 

85.3 

86.9 

88.9 

90.4 

92.5 

94.2 

95.9 

96.6 

98.0 

99.0 

122 

8.26 

75.1 

75.5 

76.6 

78.0 

78.9 

80.9 

82.4 

84.3 

85.6 

87.2 

89.2 

90.7 

92.8 

94.5 

96.2 

96.9 

98.2 

99.2 

123 

8.24 

75.3 

75.7 

76.8 

78.2 

79.1 

81.1 

82.6 

84.5 

85.8 

87.5 

89.5 

91.0 

93.0 

94.8 

96.5 

97.2 

98.5 

99.6 

124 

8.22 

75.5 

75.9 

77.0 

78.4 

79.3 

81.3 

82.8 

84.7 

86.1 

87.8 

89.8 

91.3 

93.2 

95.1 

96.8 

97.5 

98.7 

99.7 

125 

8.2 

75.7 

76.1 

77.2 

78.6 

79.5 

81.5 

83.0 

84.9 

86.3 

88.0 

90.0 

91.5 

93.4 

95.4 

97.1 

97.8 

99.0 

100.0 

126 

8.18 

75.9 

76.3 

77.4 

78.8 

79.7 

81.7 

83.2 

85.1 

86.6 

88.2 

90.2 

91.7 

93.6 

95.6 

97.4 

98.0 

99.2 

100.2 

127 

8.16 

76.1 

76.5 

77.6 

79.0 

79.9 

81.9 

83.4 

85.3 

86.8 

88.4 

90.4 

91.9 

93.8 

95.8 

97.6 

98.2 

99.5 

100.5 

128 

8.14 

76.3 

76.7 

77.8 

79.2 

80.1 

82.1 

83.6 

85.5 

87.1 

88.6 

90.6 

92.1 

94.0 

96.0 

97.8 

98.4 

99.7 

100.7 

129 

8.12 

76.5 

76.9 

78.0 

79.4 

80.3 

82.3 

83.8 

85.7 

87.3 

88.8 

90.8 

92.3 

94.2 

96.2 

98.0 

98.6 

100.0 

101.0 

130 

8.1 

76.7 

77.1 

78.2 

79.5 

80.5 

82.5 

84.0 

85.9 

87.5 

89.0 

91.0 

92.5 

94.4 

96.4 

98.2 

98.8 

100.2 

101.2 

131 

132 

133 

134 

135 

136 

137 

8.09 

8.08 

8.07 

8.06 

8.05 

76.8 

78.3 

79.6 

80.6 

82.6 

84.1 

86.1 

87.6 

89.1 

91.1 

92.7 

94.6 

96.6 

98.4 

99.0 

100.3 

101.3 

76.9 

78.4 

79.7 

80.7 

82.7 

84.2 

86.3 

87.7 

89.2 

91.2 

92.8 

94.7 

96.7 

98.5 

99.1 

100.5 

101.5 

77.0 

78.5 

79.8 

80.8 

82.8 

84.3 

86.4 

87.8 

89.3 

91.3 

92.9 

94.8 

96.9 

98.6 

99.3 

100.6 

101.6 

77.1 

7S.6 

79.9 

80.9 

82.9 

84.4 

86.5 

87.9 

89.4 

91.4 

93.0 

94.9 

97.0 

98.7 

09.4 

100.8 

101.8 

77.2 

78.7 

80.0 

81.0 

83.0 

84.5 

86.6 

88.0 

89.5 

91.5 

93.1 

95.0 

97.1 

98.8 

99.6 

100.9 

101.9 

8.04 

8.03 

77.3 

78.8 

80.1 

81.1 

83.1 

84.6 

86.7 

88.1 

89.6 

91.6 

93.2 

95.1 

97.2 

98.9 

99.7 

101.0 

102.0 

77.4 

78.9 

80.2 

81.2 

83.2 

84.7 

86.8 

88.2 

89.7 

91.7 

93.3 

95.2 

97.3 

99.0 

99.9 

101.2 

102.2 

138 

139 

140 

8.02 

77.5 

79.0 

80.3 

81.3 

83.3 

84.8 

86.9 

88.3 

89.8 

91.8 

93.4 

05.3 

97.4 

99.1 

100.0 

101.3 

102.3 

8.01 

77.5 

79.1 

80.4 

81.4 

83.4 

84.9 

87.0 

88.4 

89.9 

91.9 

93.5 

95.4 

97.6 

99.2 

100.2 

101.5 

102.5 

8.0 

77.6 

79.2 

80.5 

81.5 

83.5 

85.0 

87.1 

88.5 

90.0 

92.0 

93.6 

95.5 

97.6 

99.3 

100.3 

101.7 

102.7 

141 

142 

143 

144 

145 

146 

147 

148 

149 

150 
161 

152 

153 
1-54 

155 

156 

157 

7.99 

77.7 

80.6 

81.6 

83.6 

85.1 

87.2 

88.7 

90.2 

92.2 

93.7 

95.6 

97.8 

99.4 

100.5 

101.8 

102.8 

7.98 

7.97 

7.96 

7.95 

7.94 

7.93 

7.92 

7.91 

7.9 

7.89 

7.88 

7.87 

7.86 

7.85 

7.84 

7 

77.8 

80.7 

81.7 

83.7 

85.2 

87.3 

88.8 

90.3 

92.4 

93.9 

95.7 

97.9 

99.5 

100.6 

102.0 

103.0 

77.9 

80.8 

81.8 

82.8 

85.3 

87.4 

88.9 

90.4 

92.5 

94.0 

95.8 

98.1 

99.6 

100.8 

102.1 

103.1 

78.0 

80.9 

81.9 

83.9 

85.4 

87.5 

89.0 

90.5 

92.6 

94.2 

95.9 

98.2 

99.7 

100.9 

102.3 

103.3 

78.1 

81.0 

82.0 

84.0 

86.5 

87.6 

89.1 

90.6 

92.7 

94.3 

96.0 

98.3 

99.8 

101.1 

102.4 

103.4 

103.6 

103.7 

103.8 

103.9 
104.0 
104.1 

104.3 

104.4 

78.2 

81.1 

82.1 

84.1 

86.6 

87.7 

89.2 

90.7 

92.8 

94.4 

96.1 

98.4 

99.9 

101.2 

102.6 

78.3 

81.2 

82.2 

84.2 

85.7 

87.8 

89.3 

90.8 

92.9 

94.6 

96.2 

98.5 

100.0 

101.4 

102.7 

102.8 
102.9 
103.0 
103.1 

103.3 

103.4 

103.6 

103.7 

78.4 

81.3 

82.3 

84.3 

85.8 

87.9 

89.4 

90.9 

93.0 

94.6 

96.3 

98.6 

100.1 

101.5 

78.5 

81.4 

82.4 

S4.5 

85.9 

88.0 

89.5 

91.0 

93.1 

94.7 

96.4 

98.7 

100.2 

101.7 

101.8 
101.9 
102.0 
102.1 
102.2 

102.3 

102.4 

102.5 

'78.6 

81.5 

82.5 

84.5 

86.0 

88.1 

89.6 

91.1 

93.2 

94.8 

96.5 

98.8 

100.3 

78.7 

82.6 

84.6 

86  1 

88.2 

89.8 

91.3 

93.3 

94.9 

96.7 

99.0 

100.5 

78.8 

78.9 
79.0 

79.1 

79.2 
70  A 

82.7 

84.7 

86.2 

88.3 

90.0 

91.5 

93.4 

95.1 

96.8 

99.1 

100.6 

100.7 

100.8 
100.9 
101.0 
101.1 
101.2 

101.3 

101.4 

82.8 

84.8 

86.3 

88.4 

90.1 

91.7 

93.5 

95.2 

97.0 

99.3 

82.9 

84.9 

86M 

88.5 

90.2 

91.8 

93.6 

95.4 

97.1 

99.4 

99.5 

99.6 

99.7 

83.0 

85.0 

86.5 

88.6 

90.3 

91.9 

93.7 

95.5 

97.3 

83.1 

85.1 

86.6 

88.7 

90.4 

92.0 

93.8 

95.6 

97.4 

i03.9 

85.2 

86.7 

88.8 

90.5 

92.1 

93.9 

95.7 

97.6 

158 

159 

160 

7^82 

7.81 

7.8 

79.4 

79.5 

79.6 

83.3 

85.3 

86.8 

88.9 

90.6 

92.2 

94.0 

95.8 

97.7 

97.8 

97.9 

99.8 

99.9 
100.0 

102.6 

104.0 

. 

. 

. 

83.4 

83.5 

85.4 

85.5 

86.9 

87.0 

89.0 

89.1 

90.7 

90.8 

92.3 

92.4 

94.1 

94.2 

95.9 

96.0 

102.8 

104.2 

105.2 

310 


Table  E. — Combined  Corrective  Factors  for  Age  and  for  Longevity,  Sequoia  washingtoniana — Cont’d. 


Decade 
of  life 
f  tree. 

Estimated 
value  of 
smoothed 
curve  of 
growth 
shown  in 
figs.  35 
and  36. 

1  Groups  1-9 

161 

7.79 

79.7 

162 

7.78 

79.8 

163 

7.77 

79.9 

1G4 

7.76 

80.0 

165 

7.75 

80.1 

166 

7.74 

80.2 , 

167 

7.73 

80.3 

168 

7.72 

80.4 

169 

7.71 

80.5 

170 

7.7 

80.6 

171 

7.69 

80.7 

172 

7.68 

80.8 

173 

7.67 

80.9 

174 

7.66 

81.0 

175 

7.65 

81.2 

176 

7.64 

81.3 

177 

7.63 

81.4 

178 

7.62 

81.5 

179 

7.61 

81.6 

180 

7.6 

81.7 

181 

7.59 

81.8 

182 

7.58 

81.9 

183 

7.57 

82.0 

184 

7.56 

82.1 

185 

7.55 

82.2 

186 

7.54 

82.3 

187 

7.53 

82.4 

188 

7.52 

82.5 

189 

7.51 

82.6 

190 

7.5 

82.8 

191 

7.49 

82.9 

192 

7.48 

83.0 

193 

7.47 

83.1 

194 

7.46 

83.2 

195 

7.45 

83.3 

196 

7.44 

83.4 

197 

7.43 

83.5 

198 

7.42 

83.6 

199 

7.41 

83.7 

200 

7.4 

83.9 

201 

7.39 

84.0 

202 

7.38 

84.1 

203 

7.37 

84.2 

204 

7.36 

84.3 

205 

7.35 

84.5 

206 

7.34 

84.6 

207 

7.33 

84.7 

208 

7.32 

84.8 

209 

7.31 

84.9 

210 

7.3 

85.1 

211 

7.29 

85.2 

212 

7.28 

85.3 

213 

7.27 

85.4 

214 

7.26 

85.5 

215 

7.25 

8.").  6 

216 

7.24 

85.7 

217 

7.23 

85.8 

218 

7.22 

86.9 

219 

7.21 

86.0 

220 

7.2 

86.2 

221 

7.19 

86.3 

222 

7.18 

86.4 

223 

7.17 

86.5 

224 

7.16 

86.6 

225 

7.15 

86.8 

226 

7.14 

86.9 

227 

7.13 

87.0 

228 

7.12 

87.1 

229 

7.11 

87.2 

230 

7.1 

87.4 

231 

7.09 

87.6 

232 

7.08 

87.7 

233 

7.07 

87.8 

234 

7.06 

87.9 

235 

7.05 

88.0 

236 

7.04 

88.2 

237 

7.03 

88.3 

238 

7.02 

88.4 

239 

7.01 

88.5 

240 

7.0 

88.7 

! 

Group  15 

Group  16 

87.1 

89.3 

87.2 

89.5 

87.3 

89.6 

87.4 

89.7 

87.5 

89.8 

87.6 

89.9 

87.7 

90.0 

87.8 

90.1 

87.9 

90.2 

88.0 

90.3 

90.4 

90.5 

90.6 

90.7 

90.8 

90.9 

91.0 

91.1 

91.2 

91.3 

o 


00 

a. 

S 

(5 


o 


c. 

3 

O 

u 

O 


for  age  and  longevity. 

Estimated 
value  of 
smoothed 
curve  of 
growth 
shown  in 
figs.  35 
and  36. 

Combined  corrective  factor  for  age 
and  longevity. 

Group  21 

Group  22 

Group  23 

Group  24 

Group  25 

Groups 

26-31 

Decade 
of  life 
of  tree. 

Groups  1-9 

Group  22 

Group  23 

Group  24 

Group  25 

Groups 

26-31 

98.1 

100.2 

101.6 

103.0 

104.3 

105.3 

241 

6.99 

88.8 

111.5 

113.4 

114.5 

116.2 

117.2 

98.2 

100.3 

101.7 

103.1 

104.5 

105.5 

242 

6.98 

88.9 

111.6 

113.5 

114.6 

116.3 

117.3 

98.4 

100.5 

101.9 

103.3 

104.6 

105.6 

243 

6.07 

89.1 

111.7 

113.7 

114.8 

116.5 

117.5 

98.5 

100.6 

102.0 

103.4 

104.8 

105.8 

244 

6.96 

89.2 

111.9 

113.8 

114.9 

116.6 

117.6 

98.7 

100.7 

102.2 

103.5 

104.9 

105.9 

245 

6.95 

89.3 

112.0 

114.0 

115.1 

116.8 

117.8 

98.8 

100.8 

102.3 

103.6 

105.0 

106.0 

246 

6.94 

89.5 

112.2 

114.1 

115.2 

116.9 

117.9 

98.9 

100.9 

102.4 

103.7 

105.1 

106.1 

247 

6.93 

89.6 

112.3 

114.3 

115.4 

117.1 

118.1 

99.0 

101.0 

102.5 

103.8 

105.3 

106.3 

248 

6.92 

89.7 

112.5 

114.4 

115.6 

117.3 

118.3 

99.1 

101.1 

102.6 

103.9 

105.4 

106.4 

249 

6.9] 

89.8 

112.6 

114.6 

115.8 

117.5 

118.5 

99.2 

101.2 

102.7 

104.0 

105.5 

106.5 

250 

6.9 

90.0 

112.8 

114.7 

116.0 

117.7 

118.7 

99.4 

101.4 

102.9 

104.2 

105.6 

106.6 

251 

6.89 

90.1 

.  .  •  ■  . 

114.9 

116.2 

117.9 

118.9 

99.5 

101.5 

103.0 

104.3 

105.7 

108.7 

252 

6.88 

90.2 

115.0 

116.3 

118.0 

119.0 

99.6 

101.7 

103.2 

104.5 

105.9 

106.9 

253 

6.87 

90.4 

115.2 

116.5 

118.2 

119.2 

99.7 

101.8 

103.3 

104.6 

106.0 

107.0 

254 

6.86 

90.5 

115.3 

116.6 

118.3 

119.3 

99.8 

102.0 

103.5 

104.8 

106.2 

107.2 

255 

6.85 

90.6 

115.5 

116.8 

118.5 

119.5 

99.9 

102.1 

103.6 

104.9 

106.3 

107.3 

256 

6.84 

90.8 

115.6 

117.0 

118.7 

119.7 

100.0 

102.3 

103.7 

105.0 

106.5 

107.5 

257 

6.83 

90.9 

115.8 

117.2 

118.9 

119.9 

100.1 

102.5 

103.8 

105.1 

106.6 

107.8 

258 

6.82 

91.0 

115.9 

117.4 

119.1 

120.1 

100.2 

102.6 

103.9 

105.2 

106.8 

107.8 

259 

6.81 

91.1 

116.1 

117.6 

119.3 

120.3 

100.3 

102.7 

104.0 

105.3 

106.9 

107.9 

260 

6.8 

91.3 

116.2 

117.8 

119.5 

120.5 

100.5 

102.9 

104.2 

105.5 

107.0 

108.0 

261 

6.79 

91.4 

117.9 

119.6 

120.6 

100.6 

103.0 

104.3 

105.6 

107.1 

108.1 

262 

6.78 

91.6 

118.1 

119.8 

120.8 

100.8 

103.2 

104.5 

105.8 

107.3 

108.3 

263 

6.77 

91.7 

118.3 

120.0 

121.0 

100.9 

103.3 

104.6 

105.9 

107.4 

108.4 

264 

6.76 

91.9 

118.5 

120.2 

121.2 

101.0 

103.5 

104.8 

106.1 

107.6 

108.6 

265 

6.75 

92.0 

118.7 

120.4 

121.4 

101.2 

103.6 

104.9 

106.2 

107.7 

108.7 

266 

6.74 

92.2 

118.9 

120.6 

121.6 

101.3 

103.7 

105.1 

106.4 

107.9 

108.9 

267 

6.73 

92.3 

119.1 

120.8 

121.8 

101.5 

103.8 

105.2 

106.5 

108.0 

109.0 

268 

6.72 

92.5 

119.3 

121.0 

122.0 

101.6 

103.9 

105.4 

106.6 

108.2 

109.2 

269 

6.71 

92.6 

119.5 

121.2 

122.2 

101.8 

104.0 

105.5 

106.7 

108.3 

109.3 

270 

6.7 

92.8 

119.7 

121.4 

122.4 

101.9 

104.2 

105.7 

106.9 

108.4 

109.4 

271 

6.69 

92.9 

121.6 

122.6 

102.1 

104.3 

105.8 

107.0 

108.5 

109.5 

272 

6.68 

93.0 

121.8 

122.8 

102.3 

104.5 

106.0 

107.2 

108.7 

109.7 

273 

6.67 

93.2 

122.0 

123.0 

102.4 

104.6 

106.1 

107.3 

108.8 

109.8 

274 

6.66 

93.3 

122.2 

123.2 

102.6 

104.8 

106.3 

107.5 

109.0 

110.0 

275 

6.65 

93.4 

122.4 

123.4 

102.7 

104.9 

106.4 

107.6 

109.1 

110.1 

276 

6.64 

93.6 

122.6 

123.6 

102.9 

105.1 

106.6 

107.8 

109.3 

110.3 

277 

6.63 

93.7 

122.8 

123.8 

103.0 

105.3 

106.7 

107.9 

109.4 

110.4 

278 

6.62 

93.8 

123.0 

124.0 

103.2 

105.4 

106.9 

108.0 

109.6 

110.6 

279 

6.61 

93.9 

123.2 

124.2 

103.3 

105.5 

107.0 

108.1 

109.7 

110.7 

280 

6.6 

94.1 

123.4 

124.4 

103.5 

105.7 

107.2 

108.3 

109.9 

110.9 

281 

6.59 

94.2 

124.6 

103.6 

105.8 

107.3 

108.4 

110.0 

111.0 

282 

6..58 

94.4 

124.8 

103.8 

106.0 

107.5 

108.6 

110.2 

111.2 

283 

6.57 

94.5 

125.0 

103.9 

106.1 

107.6 

108.7 

110.3 

111.3 

284 

6.56 

94.7 

125.2 

104.1 

106.3 

107.8 

108.9 

110.5 

111.5 

285 

6.55 

94.8 

• 

125.4 

104.2 

106.4 

107.9 

109.0 

110.6 

111.6 

286 

6.54 

95.0 

125.6 

104.4 

106.6 

108.1 

109.2 

110.8 

111.8 

287 

6.53 

95.1 

125.8 

104.5 

106.7 

108.2 

109.3 

110.9 

111.9 

288 

6.-52 

95.3 

126.0 

104.7 

106.8 

108.4 

109.5 

111.1 

112.1 

289 

6.51 

95.4 

126.2 

104.8 

106.9 

108.5 

109.6 

111.3 

112.3 

290 

6.5 

95.6 

126.4 

104.9 

107.1 

108.7 

109.8 

111.4 

112.4 

291 

6.49 

95.8 

126.6 

105.1 

107.2 

108.8 

109.9 

111.5 

112.5 

292 

6.48 

95.9 

126.8 

105.2 

107.4 

109.0 

110.1 

111.7 

112.7 

293 

6.47 

96.1 

127.0 

105.4 

107.5 

109.1 

110.2 

111.8 

112.8 

294 

6.46 

96.3 

127.2 

105.5 

107.7 

109.3 

110.4 

112.0 

113.0 

295 

6.45 

96.4 

127.4 

105.6 

107.8 

109.4 

110.5 

112.1 

113.1 

296 

6.44 

96.6 

127.6 

105.7 

108.0 

109.6 

110.7 

112.3 

113.3 

297 

6.43 

96.7 

127.8 

105.8 

108.1 

109.7 

110.8 

112.5 

113.5 

298 

6.42 

96.9 

128.0 

105.9 

108.3 

109.9 

111.0 

112.7 

113.7 

299 

6.41 

97.0 

128.2 

106.0 

108.4 

110.0 

111.1 

112.8 

113.8 

300 

6.4 

97.2 

128.4 

106.1 

108.6 

110.2 

111.3 

113.0 

114.0 

301 

6.39 

97.3 

128.6 

106.3 

108.7 

110.3 

111.4 

113.1 

114.1 

302 

6.38 

97.4 

128.8 

106.4 

108.9 

110.5 

111.6 

113.3 

114.3 

303 

6..37 

97.6 

129.0 

106.6 

109.0 

110.6 

111.7 

113.4 

114.4 

304 

6.36 

97.7 

129.2 

106.7 

109.2 

110.8 

111.9 

113.6 

114.6 

305 

6.35 

97.8 

129.4 

106.9 

109.3 

110.9 

112.0 

113.7 

114.7 

306 

6.34 

98.0 

129.6 

107.0 

109.5 

111.1 

112.2 

113.9 

114.9 

307 

6.33 

98.1 

129.8 

107.2 

109.6 

111.2 

112.3 

114.0 

115.0 

308 

6.32 

98.2 

130.0 

107.4 

109.8 

111.4 

112.5 

114.2 

115.2 

309 

6.31 

98.3 

130.2 

107.5 

109.9 

111.5 

112.6 

114.3 

115.3 

310 

6.3 

98.5 

130.4 

107.7 

110.1 

111.7 

112.8 

114.5 

115.5 

311 

6.29 

98.6 

130.6 

107.8 

110.2 

111.8 

112.9 

114.6 

115.6 

312 

6.28 

98.8 

130.8 

108.0 

110.4 

112.0 

113.1 

114.8 

115.8 

313 

6.27 

98.9 

131.0 

108.1 

110.5 

112.2 

113.2 

114.9 

116.0 

314 

6.26 

99.1 

131.2 

108.3 

110.6 

112.3 

113.3 

115.0 

116.1 

315 

6.25 

99.2 

131.4 

108.4 

110.8 

112.5 

113.5 

115.2 

116.3 

316 

6.24 

99.4 

131.6 

108.6 

110.9 

112.7 

113.7 

115.4 

116.5 

317 

6.23 

99.5 

131.8 

108.7 

111.1 

112.8 

113.9 

115.6 

116.7 

318 

6.22 

99.7 

132.0 

108.9 

111.2 

113.0 

114.1 

115.8 

116.9 

319 

6.21 

99.8 

132.2 

109.0 

111.3 

113.2 

114.3 

116.0 

117.1 

320 

6.2 

100.0 

132.4 

91.2 

91.3 

91.4 

91.5 

91.6 

91.7 

91.8 

91.9 
92.0 

92.1 

92.3 

92.4 

92.3 

92.6 

92.7 

92.8 

92.9 
93.0 

93.1 

93.2 

93.4 
93.6 

93.5 

93.6 

93.7 

93.8 

93.9 
94.0 

94.2 

94.4 

94.5 

94.6 

94.7 

94.8 

94.9 
95.0 

95.1 

95.2 

95.3 

95.4 


92.6 

92.7 

92.8 

92.9 
93.0 

93.1 

93.2 

93.3 

93.4 

93.5 
93.7 

93.9 
94.0 

94.1 

94.2 

94.3 

94.4 

94.5 

94.6 

94.7 

94.9 

95.1 

95.3 

95.4 

95.5 

95.6 

95.7 

95.8 

95.9 
96.0 

96.2 
96.4 

96.6 

96.7 

96.8 

96.9 
97.0 
97.x 

97.3 

97.4 
97.6 
97.8 
98.0 

98.1 

98.2 

98.3 

98.4 

98.5 

98.6 

98.7 


94.3 

94.4 

94.5 

94.6 

94.7 

94.8 

94.9 
95.0 

95.1 

95.2 

95.3 

95.4 

95.5 

95.6 

95.7 

95.8 

95.9 
96.0 

96.1 

96.2 
96.4 
96.6 

96.8 
97.0 

97.2 

97.3 

97.4 

97.5 

97.6 

97.7 

97.9 

98.1 

98.3 

98.4 

98.5 

98.6 

98.7 

98.8 

98.9 
99.0 

99.2 
99.4. 

99.6 

99.7 

99.8 

99.9 
100.0 
100.1 
100.2 

100.3 

100.5 

100.7 

100.9 

101.1 

101.3 

101.5 

101.7 

101.9 
102.1 

102.3 


96.1 

96.2 

95.3 

96.5 

96.6 

96.7 

96.8 

96.9 
97.0 

97.1 

97.3 

97.4 

97.5 

97.7 

97.8 
98.0 

98.1 

98.3 

98.4 

98.5 

98.7 

98.8 
99.0 

99.1 

99.3 

99.4 

99.6 

99.7 

99.8 

99.9 
100.1 
100.2 

100.4 

100.5 

100.6 

100.7 

100.8 

100.9 
101.0 
101.1 

101.3 

101.4 
101.6 

101.7 

101.9 
102.0 
102.2 

102.3 

102.4 

102.5 

102.7 

102.8 
103.0 

103.1 

103.3 

103.4 

103.6 

103.7 
103.8; 

103.9 

104.1 

104.2 

104.4 

104.5 

104.7 

104.8 

104.9 
105.0 

105.1 

105.2 


Table  F. — Growth  of  Sequoia  ivashingtoniuna  hy  Groups  for  each  Decade. 


311 


Group. 

Sec  note  at  end  of  table, 
page  322.) 

1901-10 

A.D. 

^  2 
II 

1881-90 

s 

1 

00 

1.  Total  growth . 

77.5 

138.0 

177.5 

183.5 

No.  of  measurements 

3 

6 

7 

Corrected  growth .  . . 

25.8 

45.5 

57.9 

59.2 

2.  Total  growth . 

38.0 

128.0 

134.5 

146.5 

2 

7 

8 

Corrected  growth .  .  . 

14.2 

47.2 

49.0 

5^7 

3.  Total  growth . 

92.0 

237.0 

261.5 

266.0 

No.  of  measurements 

6 

13 

15 

15 

Corrected  growth .  .  . 

37.0 

95.4 

103.8 

104.2 

23  5 

163.0 

580.0 

742.0 

No.  of  measurements 

2 

10 

48 

63 

Corrected  growth.  .  . 

11.2 

76.5 

269.0 

339.0 

5.  Total  growth . 

00.0 

203.0 

234.5 

241.0 

No.  of  measurements 

8 

15 

20 

21 

Corrected  growth .  .  . 

32.0 

109.0 

124.5 

126.0 

0.  Total  growth . 

17.5 

60.5 

92.0 

92.0 

No.  of  measurements 

2 

7 

10 

10 

Corrected  growth .  .  . 

10.7 

36.5 

55.0 

54.3 

44.5 

152.5 

161.5 

No.  of  measurements 

4 

15 

17 

29.0 

98.5 

103.8 

8.  Total  growth . 

34.0 

148.5 

304.5 

285.5 

No.  of  measurements 

4 

13 

25 

26 

Corrected  growth.  .  . 

23.3 

101.5 

207.0 

193.3 

359.5 

441.0 

423.5 

No.  of  measurements 

28 

41 

41 

254.0 

309.0 

296.0 

10.  Total  growth . 

30.0 

347.0 

449.0 

437.0 

No.  of  measurements 

3 

34 

42 

Corrected  growth .  .  . 

22.2 

330.5 

330.5 

322.0 

456.5 

691.5 

668.0 

No.  of  measuremeuts 

51 

72 

74 

353.0 

532.0 

513.0 

12.  Total  growth . 

40.5 

425.0 

612.5 

702.0 

No.  of  measurements 

4 

43 

54 

59 

Corrected  growth.  .  . 

32.4 

340.0 

488.0 

.558.0 

13.  Total  growth . 

77.5 

363.0 

452.0 

421.5 

No.  of  measurements 

o 

37 

49 

49 

Corrected  growth.  .  . 

03.0 

298.5 

370.0 

.345.0 

14.  Total  growth . 

48.0 

393.5 

518.5 

492.0 

No.  of  measurements 

3 

39 

51 

51 

Corrected  growth.  .  . 

40.9 

335.0 

432.0 

418.0 

334.5 

385.5 

392.0 

38 

47 

47 

Corrected  growth.  .  . 

293.0 

337.0 

342.0 

238.0 

311.5 

288.5 

No.  of  measurements 

23 

33 

33 

Corrected  growth .  .  . 

216.0 

282.0 

261.0 

250.0 

.304.5 

334.0 

36 

42 

47 

234.0 

285.0 

311.0 

222.0 

259.0 

257.0 

No.  of  measurements 

24 

27 

30 

212.5 

249.0 

247.0 

140.5 

164.0 

184.0 

No.  of  measurements 

19 

25 

25 

140.0 

163.5 

183.0 

20.  Total  growth . 

35.0 

357.5 

433.5 

395.5 

No.  of  measurements 

2 

38 

49 

49 

Corrected  growth .  .  . 

36.0 

369.0 

447.0 

410.0 

141.0 

156.5 

146.5 

No.  of  measurements 

14 

17 

17 

149.5 

166.0 

155.0 

100.0 

180.5 

181.0 

14 

24 

110.0 

199.0 

199.0 

103.5 

95.0 

6 

11 

21.8 

117.5 

107.6 

20.0 

18.5 

19.0 

2 

Corrected  growth .  .  . 

23.4 

21.6 

22.0 

36.5 

31.5 

30.5 

4 

43.7 

37.6 

36.4 

37.0 

39.5 

41.0 

No.  of  measurements 

4 

5 

5 

Corrected  growth .  .  . 

45.8 

48.8 

.50.7 

14.5 

15.0 

13.5 

2 

18.1 

18.7 

16.8 

4.5 

4.0 

1 

1 

5.4 

4.8 

13.5 

16.5 

2 

2 

Corrected  growth .  .  . 

. 

. 

16.2 

19.8 

o 

Y 

3 

00 

1 

lO 

00 

o 

lO 

1 

s 

o 

T 

S 

o 

7 

M 

00 

o 

1 

wH 

s 

o 

1 

o 

00 

wH 

o 

00 

o 

00 

1 

rsa 

o 

1 

'O 

t> 

o 

? 

w> 

o 

■? 

o 

T 

•H 

o 

fO 

b- 

o 

M 

i 

b. 

w 

o 

T 

o 

b. 

153.0 

173.0 

141.0 

188.0 

177.0 

136.5 

176.0 

160.0 

178.0 

143.5 

124.0 

127.5 

133.5 

118.5 

124.5 

151.0 

104.5 

58.3 

160.5 

54.6 

160.0 

44.1 

134.0 

58.3 

125.5 

54.3 

116.0 

41.5 

131.0 

53.0 

115.5 
8 

38.4 

353.5 

47.7 

114.0 

52.5 

135.0 

41.8 

138.5 

35.8 

167.5 

36.4 

152.0 

37.8 

130.0 

33.0 

129.0 

34.1 

131.5 

40.7 

153.0 

43.5 

121.0 

8 

36.4 

407.6 

57.9 

283.5 

56.3 

295.5 

46.7 

267.5 

43.1 

279.0 

39.5 

256.5 

44.2 

308.0 

37.6 

335.0 

44.0 

323.0 

44.7 

334.0 

53.5 

334.0 

48.0 

366.0 

40.7 

408.5 

40.0 

414.5 

40.4 

406.0 

46.6 

409.5 

110.0 

694.5 

113.5 

687.5 

101.8 

703.5 

105.1 

714.0 

96.0 

673.5 

113.6 

694.0 

128.9 

769.5 

120.5 

754.0 

11.5.0 

737.0 

117.2 

729.0 

116.1 

780.0 

125.8 

781.0 

139.3 

825.0 

1.39.6 

831.0 

135.0 

876.5 

13.io 

800.5 

132.8 

851.0 

314.0 

262.5 

21 

135A 

89.0 

306.0 

269.0 

311.0 

269.0 

311.0 

2G8.0 

389.0 

282.5 

296.0 

285.0 

324.0 

287.5 

314.0 

288.0 

.305.0 

304.0 

298.0 

331.5 

313.0 

345.5 

310.0 

353.5 

324.0 

360.0 

323.0 

363.0 

337.0 

381.0 

307.0 

3C5.5 

321.0 

375.0 

135.3 

92.5 

135.0 

99.0 

132.5 

89.5 

138.0 

91.0 

137.5 

95.0 

136.5 

102.0 

135.0 

101.0 

141.0 

103.5 

151.0 

99.0 

156.0 

109.0 

157.5 

108.5 

159.0 

127.5 

158.0 

141.0 

163.5 . 
129.5 

155.5 

138.0 

158.0 

115.5 

52.1 

160.5 
17 

102.7 

292.5 
26 

197.0 

474.0 

42 

329.0 

429.0 

53.5 

163.5 

56.8 

157.0 

50.6 

149.5 

50.8 

148.0 

52.3 

155.0 

55.5 

173.0 

54.2 

170.0 

55.0 

167.0 

51.8 

180.5 

56.4 

155.0 

55.2 

170.5 

63.9 

188.5 

69.6 

176.0 

63.2 

199.0 

66.4 

188.5 

54.9 

172.5 

104.3 

264.0 

99.5 

279.0 

94.3 

288.0 

92.6 

291.5 

96.3 

310.5 

106.4 

282.0 

103.4 

297.0 

100.8 

283.0 

107.8 

286.5 

88.6 

283.5 

99.9 

275.5 

109.0 

281.0 

101.0 

299.0 

112.6 

322.5 

105.2 

311.0 

9.5.1 

286.0 

177.5 

450.0 

186.8 

424.5 

192.0 

403.0 

193.5 

412.0 

205.0 

418.0 

185.3 

443.5 

194.0 

418.5 

184.0 

390.5 

185.0 

421.5 

182.5 

416.0 

176.5 

471.0 

179.3 

481.0 

189.5 

472.0 

203.2 

449.0 

195.0 

455.5 

177.7 

406;0 

311.5 

418.5 

292.5 

395.5 

276.5 

410.5 

281.0 

384.0 

285.0 

431.0 

300.5 

438.5 

282.5 

431.5 

262.5 

419.0 

282.0 

413.5 

278.0 

4.30.5 

312.0 

401.5 

317.5 

409.5 

310.0 

448.0 

293.5 

444.0 

296.0 

427.5 

301.0 

407.0 

314.0 

641.0 

74 

491.0 

651.0 

306.0 

677.5 

75 

517.0 

702.0 

288.0 

715.5 

75 

545.0 

612.0 

297.0 

719.0 

287.0 

712.0 

309.0 

747.0 

313.0 

733.5 

306.0 

730.0 

296.0 

713.5 

290.0 

782.5 

301.0 

743.0 

379.0 

773.5 

383.0 

786.5 

308.0 

755.5 

302.0 

726.5 

292.0 

768.5 

277.0 

708.5 

546.0 

623.0 

539.0 

612.5 

565.0 

632.0 

552.0 

630.5 

547.0 

601.0 

533.0 

593.5 

583.0 

593.5 

552.0 

595.0 

572.0 

655.0 

580.0 

680.0 

555.0 

654.5 

531.0 

616.0 

558.0 

586.5 

513.0 

582.5 

518.0 

400.0 

557.0 

431.0 

485.0 

430.0 

493.0 

406.0 

484.0 

436.0 

497.0 

445.0 

496.0 

503.0 

472.0 

431.5 

464.0 

400.5 

463.0 

431.0 

463.0 

407.5 

507.0 

428.5 

524.0 

429.0 

503.0 

432.5 

473.0 

417.5 

448.0 

421.0 

443.0 

425.5 

327.0 

484.5 

352.0 

496.0 

351.0 

450.5 

331.0 

476.5 

354.0 

472.5 

3^.0 

481.5 

408.0 

504.5 

3k).b 

476.5 

324.0 

483.0 

349.0 

473.0 

329.0 

462.5 

346.0 

490.0 

346.0 

496.0 

348.0 

532.0 

335.0 

498.0 

337.0 

478.5 

340.0 

467.5 

410.0 

363.5 

411.0 

369.5 

381.0 

369.5 

402.0 

375.5 

399.0 

387.5 

407.0 

394.5 

425.0 

382.0 

401.0 

376.5 

406.0 

385.0 

396.0 

401.5 

390.0 

395.0 

410.0 

387.5 

415.0 

400.5 

444.0 

391.5 

415.0 

365.0 

399.0 

370.0 

388.0 

386.5 

316.5 

252.5 

321.0 

249.5 

321.0 

233.0 

328.0 

247.5 

336.0 

240.5 

342.0 

246.0 

330.5 

259.5 

325.0 

271.5 

3.32.5 

280.0 

346.5 

256.0 

340.0 

233.0 

334.0 

240.5 

344.0 

232.5 

336.0 

239.0 

313.0 

231.5 

317.0 

237.5 

331.0 

236.0 

228.0 

342.0 

225.0 

337.0 

210.0 

358.0 

223.0 

332.0 

216.0 

330.5 

221.0 

351.0 

232.5 

347.5 

243.0 

337.5 

250.5 

310.0 

229.0 

339.0 

207.0 

310.5 

214.0 

337.0 

207.0 

360.0 

212.0 

336.5 

205.5 

363.5 

210.5 

3ol.o 

204.0 

354.0 

319.0 

274.0 

30 

264.0 

177.0 

314.0 

246.0 

334.0 

252.5 

308.5 

250.5 

307.0 

259.0 

325.5 

258.5 

322.0 

269.5 

307.0 

244.5 

287.0 

241.0 

308.0 

260.5 

287.0 

244.5 

306.0 

255.0 

330.5 

271.5 

305.5 

287.5 

334.0 

279.5 

321.4 

244.0 

324.0 

245.0 

236.0 

192.5 

242.0 

193.5 

240.5 

195.0 

248.0 

187.5 

247.5 

196.0 

257.0 

204.5 

232.0 

210.5 

229.0 

198.5 

247.5 

201.0 

232.0 

199.0 

242.0 

197.5 

257.0 

201.5 

272.0 

199.5 

256.0 

203.5 

229.0 

209.0 

230.0 

217.5 

176.0 

397.0 

191.0 

406.0 

192.0 

417.0 

193.0 

432.0 

185.0 

397.5 

193.0 

425.5 

201.0 

412.5 

207.0 

425.5 

194.5 

399.5 

197.0 

414.5 

194.5 

402.5 

193.0 

405.0 

196.5 

406.0 

194.5 

394.0 

198.0 

400.5 

203.0 

393.0 

211.5 

389.5 

407.0 

128.5 

416.0 

136.5 

428.0 

141.0 

443.0 

141.0 

407.0 

140.0 

435.0 

157.5 

420.0 

158.0 

433.0 

147.0 

405.0 

141.5 

420.0 

137.0 

407.5 

134.5 

409.0 

130.0 

410.0 

130.5 

398.0 

131.5 

404.0 

148.0 

396.0 

147.0 

392.0 

148.0 

136.0 

189.5 

144.5 

178.0 

149.0 

185.0 

149.0 

187.5 

148.0 

165.0 

165.5 

169.5 

166.0 

176.5 

154.0 

184.0 

148.5 

166.0 

143.5 

182.5 

141.0 

183.0 

136.0 

186.0 

136.0 

171.5 

136.5 

176.0 

153.0 

178.5 

152.0 

186.5 

153.5 

179.5 

197.5 

lOO.O 

196.0 

99.0 

203.0 

96.5 

205.5 

100.0 

181.0 

96.0 

185.5 

92.5 

192.5 

96.5 

200.5 

86.0 

181.0 

78.5 

198.5 

76.5 

199.0 

78.0 

202.0 

78.0 

186.0 

71.0 

190.0 

66.5 

192.5 

65.0 

201.0 
76. 5 

193.0 

84.0 

113.2 

18.0 

111.8 

17.5 

108.7 

21.5 

112.7 

15.0 

108.0 

18.5 

104.0 

19.0 

108.5 

15.5 

96.4 

14.0 

87.7 

16.5 

85.5 

19.0 

87.0 

18.5 

87.0 

18.5 

79.0 

16.5 

74.0 

20.5 

72.0 

18.5 

84.7 

13.5 

94.0 

11.0 

20.9 

30.5 

20.2 

30.5 

24.9 

31.0 

18.0 

34.5 

21.4 

36.0 

22.0 

38.5 

17.8 

41.5 

16.1 

36.5 

18.9 

30.5 

21.8 

37.0 

21.2 

34.5 

21.2 

33.5 

18.8 

34.5 

13.3 

25.5 

21.0 

24.0 

15.2 
26  5 

12.4 

37.0 

36.3 

43.0 

36.2 

40.5 

36.8 

37.0 

40.9 

39.5 

42.6 

33.5 

46.5 

30.5 

49.0 

31.5 

43.0 

34.5 

35.9 

35.0 

43.4 

35.5 

40.4 

36.5 

39.1 

32.0 

40.3 

30.5 

29.7 

32.5 

28.0 

36.0 

30.9 

37.5 

43.0 

37.5 

53.0 

15.0 

49.8 

16.0 

45.4 

16.0 

48.4 

14.0 

41.0 

11.0 

37.3 

12.5 

38.4 

12.0 

42.0 

10.5 

42.6 

13.5 

43.2 

14.0 

44.3 

13.0 

38.7 

12.5 

36.9 

12.5 

39.2 

19.0 

43.4 

18.0 

45.0 

15.0 

45.0 

15.5 

18.7 

4.0 

20.0 

3.0 

20.0 

4.0 

17.5 

4.5 

13.6 

4.5 

15.5 

6.0 

14.8 

5.0 

13.0 

5.0 

15.3 

4.0 

17.3 

4.5 

16.0 

4.0 

15.3 

4.5 

15.3 

6.5 

23.3 

6.5 

22.0 

5.0 

18.3 

5.0 

18.9 

4.0 

4.8 

1 

10.8 

16.0 

3.6 

7.0 

1 

8.4 

13.5 

4.8 

9.5 

5.4 

7.5 

5.4 

9.5 

7.2 

10.5 

6.0 

8.5 

6.0 

10.0 

4.8 

8.5 

5.4 

7.0 

4.8 

9.0 

5.4 

10.0 

6.6 

10.0 

7.8 

10.0 

6.0 

8.0 

6.0 

9.5 

4.8 

9.5 

11.4 

13.0 

9.0 

13.5 

11.4 

12.0 

12.6 

10.0 

10.2 

12.5 

12.0 

14.5 

10.2 

12.5 

8.4 

12.0 

10.8 

12.5 

12.0 

10.0 

12.0 

9.0 

12.0 

10.0 

9.6 

13.5 

11.4 

9.5 

11.4 

8.5 

19.2 

16.2 

15.6 

16.2 

14.4 

12.0 

15.0 

17.4 

15.0 

14.4 

15.0 

12.0 

10.8 

12.0 

16.2 

11.4 

10.2 

312  Table  F. — Growth  of  Sequoia  washingloniana,  by  Groups  for  each  Decade — Continued. 


Group. 

1691- 
1700  A.D. 

06-1891 

o 

00 

1 

o 

1661-70 

? 

v> 

'O 

1641-50 

1 

? 

o 

1621-30 

1611-20 

1601-10 

^  s 

in  S 

06-183 I 

1571-80 

1 

1561-70 

m 

in 

j  1541-50 

1531-40 

1521-30 

1511-20 

Ot-IOSl 

133.0 

7 

34.3 

1.50.5 

8 

44.8 

431.5 
15 

139.1 

890.0 

03 

333.0 

337.5 
21 

141.0 

109.0 

10 

51.1 

192.5 
17 

104.7 

314.5 
26 

193.5 

489.5 
42 

315.0 

409.C 

42 

277.0 

771.0 

75 

555.0 

611.5 
59 

465.0 

427.5 
49 

340.0 

480.0 

51 

399.0 

412.0 

47 

352.0 

241.0 

33 

213.0 

343.0 

47 

312.5 
273.0 

30 

255.0 

217.5 
25 

211.5 
417.0 

49 

419.0 

171.5 
17 

176.5 
173.0 

24 

186.0 

80.6 

11 

89.0 

15.0 

2 

16.9 
34.0 

4 

39.5 
38.0 

5 

45.6 
16.5 

2 

20.1 
4.0 

1 

4.8 
6.5 

1 

7.8 
9.0 
2 

10.8 

133.5 

7 

33.6 

166.0 

82.0 

6 

20.0 

171.5 

56.5 

5 

13.9 

153.0 

60.5 

5 

140.3 

150.6 

51.0 

4 

11.5 

148.0 

No.  of  measurements 
Coixected  growth . .  , 

2.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . 

140.0 

147.5 

149.5 

110.5 
8 

29.2 

444.5 

120.0 

7 

31.0 

298.5 

121.5 

7 

30.6 

318.0 

61.0 

5 

15.4 

283.6 

7  7.5 
5 

19.5 

375.0 

73.0 

4 

18.4 

354.0 

44.5 

3 

11.0 

314.6 

53.5 
3 

12.6 
328.0 

41.5 

2 

9.8 

314.0 

34.0 

2 

7.7 

292.0 

48.9 

404.0 

SO.O 

435.0 

44.2 

429.5 

43.0 

393.0 

41.8 

384.0 

39.0 

395.0 

40.5 

381.5 

40.2 

382.5 

275.5 

15 

69.4 

1300.0 

No.  of  measurements 
Corrected  growth . .  . 

4.  Total  growth . 

No.  of  measurements 
Corrected  growth. . . 

129.0 

940.5 

137.2 

940.0 

134.1 

883.0 

121.8 

925.5 

117.8 

963.0 

120.0 

953.0 

114.6 

987.0 

113.8 

1038.0 

131.0 

1048.0 

87.0 

1000.0 

91.9 

1010.5 

81.2 

1005.5 

106.3 

1134,5 

98.6 

1159.0 

86.1 

1137.5 

88.3 

1224.0 

82.9 

1204.0 

75.3 

1250.5 

347.0 

325.0 

343.0 

343.5 

318.0 

332.0 

3.30.0 

324.5 

338.0 

369.0 

332.0 

343.5 

339.0 

354.5 

354.0 

360.5 

353.0 

367.0 

333.6 

401.0 

334.0 

409.0 

347.0 

429.0 

366.0 

425.6 

370.0 

421.0 

359.0 

391.5 

380.0 

445.5 

373.0 

462.5 

384.0 

441.5 

395.0 

430.0 

No.  of  measurements 
Corrected  growth . .  . 

134.0 

121.0 

140.0 

118.0 

133.0 

127.0 

128.5 

135.5 

144,5 

129.0 

133.2 

125.0 

136.0 

139.5 

137.0 

130.0 

138.5 

118.5 

150.0 

133.5 

151.0 

158.5 

156.5 

165.0 

153.0 

178.5 

iso.0 

169.5 

138.0 

180.0 

155.0 

165.0 

159.0 

180.0 

150.5 

180.0 

145.0 

174.0 

No.  of  measurements 
Corrected  growth . . . 

56.2 

182.0 

53.8 

201.0 

57.3 

213.0 

60.3 

206.0 

57.0 

208.0 

54.4 

192.5 

59.8 

215.0 

55.3 

227.6 

60.0 

199.0 

65.6 

197.0 

65.5 

194.0 

67.3 

210.5 

71.7 

206.0 

63.3 

193.5 

70.6 

222.5 

64.0 

216.0 

69.0 

224.5 

68.4 

213.5 

65.6 

215.0 

No.  of  measurements 
Corrected  growth . . . 

97.6 

348.5 

105.5 

356.0 

111.4 

333.5 

105.9 

325.5 

106.7 

322.5 

98.6 

312.5 

106.4 

322.0 

111.6 

352.6 

95.9 

328.5 

93.6 

328.0 

91.1 

306.5 

97.6 

345.5 

94.1 

343.5 

87.3 

333.5 

100.3 

331.0 

95.4 

333.0 

97.5 

334.0 

91.8 

368.0 

91.5 

348.5 

No.  of  measurements 
Corrected  growth. . . 

212.2 

471.5 

214.8 

470.5 

199.0 

462.0 

192.3 

466.5 

188.5 

462.5 

181.0 

507.0 

184.8 

496.5 

199.3 

521.5 

183.3 

535.5 

180.8 

6C6.5 

166.7 

475.3 

185.5 

513.0 

182.0 

505.5 

175.0 

520.5 

159.0 

542.0 

167.5 

54.5.5 

167.5 

525.5 

181.8 

530.0 

170.5 

544.0 

No.  of  measurements 
Corrected  growth . . . 

302.C 

429.5 

300.0 

444.0 

292.5 

454.0 

294.0 

430.5 

288.5 

412.0 

313.0 

437.5 

304.0 

453.0 

316.0 

454.0 

321.3 

462.5 

300.5 

462.0 

280.0 

473.5 

298.0 

605.0 

291.0 

403.0 

298.3 

600.0 

304.0 

470.5 

302.2 

457.0 

287.5 

440.0 

286.5 

472.0 

290.0 

446.5 

No.  of  measurements 
Corrected  growth . . . 

303.5 

794.5 

"298.5 

794.0 

304.0 

813.5 

287.0 

850.0 

273.0 

887.6 

289.0 

845.5 

297.0 

883.0 

296.5 

852.0 

301.0 

810.0 

298.0 

828.0 

304.0 

S67.0 

323.0 

821.0 

313.0 

863.0 

317.0 

847.6 

296.0 

865.5 

285.0 

830.5 

272.0 

827.0 

288.0 

816.5 

270.5 

763.0 

No.  of  measurements 
Corrected  growth . . . 

569.0 

639.5 

565.0 

649.0 

577.0 

651.0 

599.0 

664.0 

623.0 

710.5 

590.0 

697.0 

615.0 

663.5 

590.0 

656.0 

658.0 

620.5 

568.0 

621.0 

594.0 

621.0 

559.0 

627.0 

586.0 

610.0 

572.0 

600.0 

583.0 

624.0 

557.0 

699.5 

650.0 

625.5 

642.0 

633.0 

503.0 

631.5 

No.  of  measurements 
Corrected  growth . . . 

485.0 

424.0 

49C.0 

430.0 

489.0 

412.0 

497.0 

396.5 

530.0 

404.5 

517.0 

414.5 

483.0 

430.0 

483.0 

442.0 

454.0 

424.5 

452.0 

417.5 

450.0 

425.5 

452.0 

446.5 

437.0 

440.0 

427.0 

430.0 

442.0 

440.5 

427.0 

429.0 

440.0 

418.5 

443.0 

436.5 

442.0 

401.0 

No.  of  measurements 
Corrected  growth . . . 

337.0 

615.5 

341.0 

520.0 

326.0 

617.0 

313.0 

498.0 

318.0 

481.5 

325.0 

452.0 

337.0 

471.0 

346.0 

467.5 

330.0 

463.5 

324.0 

502.5 

329.0 

467.0 

344.0 

505.0 

338.0 

475.5 

329.0 

471.0 

335.0 

463.5 

325.0 

465.5 

316.0 

479.0 

328.0 

477.0 

300.0 

464.5 

No.  of  measurements 
Corrected  growth . . . 

428.0 

399.0 

431.0 

391.0 

428.0 

382.5 

413.0 

365.0 

398.0 

368.0 

372.0 

385.C 

388.0 

382.0 

384.0 

389.5 

380.0 

400.5 

410.6 

391.5 

380.0 

406.0 

410.0 

386.5 

386.0 

411.0 

380.0 

355.0 

373.0 

378.5 

373.0 

364.0 

383.0 

372.5 

380.0 

375.0 

369.0 

353.0 

No.  of  measurements 
Corrected  growth _ 

441.0 

251.6 

. 

.333.0 

243.0 

325.0 

262.5 

311.0 

253.5 

313.0 

255.0 

326.5 

266.0 

324.0 

276.5 

330.0 

285.5 

339.0 

2V0.5 

331.0 

287.0 

342.0 

268.5 

326.0 

273.5 

346.0 

276.0 

298.5 

269.0 

318.0 

277.5 

305.0 

258.0 

311.5 

257.5 

313.0 

263.5 

294.0 

242.0 

No.  of  measurements 
Corrected  growth . . . 

222.0 

342.5 

214.0 

346.5 

231.0 

346.5 

223.0 

367.5 

224.0 

355.0 

234,0 

357.0 

243.0 

378.5 

250.0 

358.5 

237.0 

350.5 

251.0 

319.5 

234.5 

355.5 

238.5 

365.0 

241.0 

375.0 

234.0 

384.0 

241.0 

364.5 

234.0 

348.5 

223.0 

327.5 

228.0 

324.5 

209.6 

296.5 

No.  of  measurements 
Corrected  growth _ 

312.0 

250.0 

316.0 

271.5 

316.0 

280.0 

.334.0 

267.0 

322.0 

260.0 

324.0 

243.5 

342.5 

247.5 

325.5 

238.5 

316.0 

236.0 

288.0 

229.5 

317.5 

243.0 

327.6 

227.0 

336.5 

224.0 

344.0 

212.0 

320.0 

215.5 

312.0 

225.G 

293.0 

220.0 

290.0 

213.5 

264.0 

194.0 

No.  of  measurements 
Corrected  growth . . . 

19.  Total  growth . 

No.  of  measurements 
Corrected  growth. . . 

235.0 

220.0 

25-4.0 

213.5 

262.0 

211.5 

250.0 

210.0 

243.0 

202.0 

226.5 

212.5 

230.0 

218.6 

222.0 

198.0 

219.5 

192.0 

.  213.0 
188.5 

225.6 

192.0 

211.0 

167.0 

208.0 

174.5 

196.0 

167.0 

198.5 

173.0 

208.0 

190.0 

201.5 

156.5 

196.0 

210.0 

177.0 

193.0 

213.5 

436.5 

206.5 

399.0 

204.0 

398.5 

202.5 

381.0 

192.0 

392.5 

204.5 

385.5 

210.0 

390.5 

190,0 

393.0 

184.0 

404.5 

180.5 

411.0 

184.0 

398.0 

159.0 

420.0 

166.5 

418.0 

159.0 

407.5 

164.5 

407.0 

181.0 

424.5 

177.0 

419.5 

200.0 

378.0 

183.0 

375.5 

No.  of  measurements 
Corrected  growth . . . 

438.0 

159.5 

399.5 

148.5 

399.0 

141.5 

380.0 

145.0 

391.0 

144.5 

384.0 

161.0 

388.0 

147.5 

390.0 

152.0 

«2.0 

154.5 

408.0 

138.0 

394.0 

159.5 

415.0 

132.5 

413.0 

147.0 

402.6 

132.5 

400.0 

128.0 

417.0 

137.5 

411.0 

138.5 

371.0 

129.5 

388.0 

120.5 

No.  of  measurements 
Corrected  growth . . . 

163.5 

179.0 

152.6 

183.5 

145.0 

185.5 

148.5 

177.5 

147.5 

194.0 

164.5 

184.5 

150.5 

180.0 

155.0 

186.5 

l.=>7.5 

175.0 

140.5 

175.0 

162.5 

169.0 

135.0 

172.0 

149.0 

177.5 

134.5 

184.0 

129.5 

177.0 

139.0 

168.0 

139.6 

166.5 

130.5 

159.5 

121.0 

1G4.5 

No.  of  measurements 
Corrected  growth , . . 

192..5 

83.0 

197.0 

79.5 

199.0 

83.0 

189.5 

82.0 

207.0 

84.0 

197.0 

86.0 

192.0 

81.0 

198.5 

79.5 

186.0 

75.5 

185.5 

82.5 

179.0 

88.0 

182.0 

81.5 

187.5 

85.0 

194.0 

91.0 

186.0 

92.0 

177.0 

85.5 

174.5 

81.0 

167.0 

75.5 

171.5 

76.5 

No.  of  measurements 
Corrected  growth . . . 

91.6 

1.5.5 

87.7 

14.0 

91.4 

13.0 

90.1 

13.5 

92.3 

11.5 

94.4 

12.5 

8^7 

13.0 

87.0 

12.5 

82.5 

13.5 

89.7 

13.5 

96.7 

13.5 

88.5 

10.5 

92.2 

11.0 

98.8 

12.0 

99.5 

12.5 

92.5 

14,0 

87.5 

12.5 

81.4 

16.0 

82.3 

12.0 

No.  of  measurements 
Corrected  growth . . , 
25.  Total  growth . 

17.5 

35.0 

15.7 

32.5 

14.6 

35.0 

15.0 

38.0 

12.9 

31.5 

14  0 
37.0 

14.5 

34.0 

14.0 

36.5 

15.1 

36.5 

15.1 

39.5 

15.1 

37.5 

n.7 

38.5 

12.2 

44,0 

13.3 

40.0 

13.8 

37.0 

15.4 

35.0 

13.8 

32.5 

17.6 

35.5 

13.2 

27.5 

No.  of  measurements 
Corrected  growth . . . 
26.  Total  growth . 

40.5 

44.5 

37.5 

39.5 

40.4 

40.0 

43.8 

40.5 

36.3 

34.0 

42.5 

40.0 

39.0 

36.5 

41,8 

41.0 

41.8 

38.0 

45.2 

34.0 

42.6 

34.5 

43.8 

37.5 

49.8 

37.0 

45.5 

30.0 

42.0 

45.5 

39.7 

38.5 

37.0 

36.5 

40.2 

36.5 

31.2 

33.5 

No.  of  mcMurements 
Corrected  growth . . . 
27.  Total  growth . 

53.3 

11.5 

47.2 

15.5 

47.7 

13.0 

48.3 

14.0 

40.4 

13.0 

47.6 

12.0 

43.3 

12.5 

48.6 

12.0 

45.0 

11.5 

40.2 

12.0 

40.7 

12.0 

44.1 

12.0 

43.5 

12.0 

45.8 

13.5 

53.4 

10.0 

45.1 

12.0 

42.7 

12.6 

42.6 

12.0 

39.0 

10.0 

No.  of  measurements 
Corrected  growth . .  . 

J  28  Total  growth . 

&  No.  of  meas’ments 
1 29  Corrected  growth . 
30.  Total  growth . 

14.0 

4.0 

18.8 

4.5 

15.7 

3.5 

16.9 

6.0 

15.7 

5.5 

14.5 

4.5 

15.1 

5.5 

14.4 

4.0 

13.8 

4.5 

14.4 

4.5 

14.3 

5.0 

14.3 

9.5 

14.3 

2.0 

15.1 

7.0 

11.9 

5.5 

14.2 

6.5 

14.8 

6.5 

14.2 

6.5 

11.8 

6.0 

4.8 

5.5 

5.4 

8.0 

4.2 

10.0 

7.2 

9.5 

6  6 
8.0 

5.4 

10.5 

6.0 

10.0 

4.8 

14.0 

5.4 

14.0 

5.4 

16.0 

6.0 

18.0 

11.4 

12.0 

2.4 

17.0 

8.4 

12.0 

6.6 

8.0 

7.8 

8.0 

7.8 

9.0 

7.8 

7.6 

7.2 

10.0 

No.  of  measurements 
Corrected  growth . . . 

31.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . 

6.6 

10.0 

9.6 

11.5 

12  0 
13.0 

11.4 

13.0 

9.6 
14  0 

12.6 

14..'; 

12.0 

13.0 

16.8 

13.5 

16.8 

11.5 

19.2 

13.5 

21.6 

13.0 

14.4 

13.0 

20.4 

13.0 

14.4 

14.5 

9.6 

12.6 

9.6 

16.0 

10.8 

16.5 

9.0 

17.5 

12.0 

16.0 

12.0 

13.8 

15.6 

16.2 

16.8 

17.4 

15.6 

16,2 

13.8 

16.3 

15.6 

15.6 

15.6 

17.4 

15.6 

19.2 

19.8 

21.0 

19.2 

Table  F. — Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade — Continued 


313 


Group. 

1491- 

1500 A.D 

0 

'T 

5 

•i>4 

1  1471-80 

1461-70 

1451-60 

1441-50 

1431-40 

1421-30 

1411-20 

0 

7 

s 

1391- 
1  1400 

? 

00 

1371-80 

1 

'  1361-70 

0 

? 

in 

w>l 

1341-SO 

1331-40 

1321-30 

1311-20 

1301-10 

3.  Total  growth . 

201.5 
11 
51.9 

1267.0 

63 

381.0 

437.0 

21 

145.5 

173.5 
10 

64.8 

209.5 
17 

88.4 

320.5 
26 

154.0 

547.0 

42 

287.6 
455.0 

42 

287.0 

742.5 
75 

487.0 

601.0 

59 

418.0 

411.5 
49 

307.0 

449.0 

51 

355.0 

352.5 
47 

293.0 

253.5 
33 

219.0 

298.0 

47 

266.0 

204.5 
30 

187.0 

199.0 

25 

189.0 

367.0 

49 

358.0 

124.5 
17 

125.0 

148.5 
24 

155.5 

71.5 
11 
77.0 

14.5 
2 

14.8 

30.5 

4 

34.4 
36.0 

5 

41.9 

13.5 
2 

15.9 
4.0 
1 

4.8 

10.0 

1 

12.0 

11.0 

2 

13.2 

184.5 

10 

46.5 

1271.0 

163.5 

8 

41.2 

1224.5 

54.0 

4 

14.1 

1377.0 

60.5 

4 

13.0 

1494.5 

57.5 

4 

14.3 

1661.5 

76.0 

4 

18.2 

1655.0 

103.5 

4 

23.8 

1759.0 

66.0 

2 

14.8 

1849.5 

No.  of  measurements 
Corrected  growth. . . 

1932.5 

1992.5 

63 

526.0 

443.0 

2044.5 

63 

527.6 

494.0 

2248.5 

60 

566.0 

515.0 

2256.0 

60 

555.0 

524.5 

2072.0 

50 

510.0 

557.0 

1956.5 

44 

464.0 

608.5 

1G15.0 

34 

381.0 

593.0 

659.5 
12 

155.6 
608.5 

341.0 

5 

80.5 

465.0 

227.0 

3 

51.1 

427.0 

21 

114.8 

222.0 

No.  of  measurements 
Corrected  growth. . . 

379.0 

378.0 

361.0 

381.0 

402.0 

412.0 

432.0 

430.0 

472.6 

407.5 

468.0 

454.5 

491.0 

448.5 

506.0 

476.0 

620.0 

472.5 

No.  of  measurements 
Corrected  growth. . . 

125.0 

176.0 

124.5 

172.0 

133.0 

163.0 

137.0 

177.5 

129.0 

182.5 

142.0 

196.5 

139.0 

221.0 

146.0 

220.5 

143.5 

209.5 

133.5 

229.5 

147.0 

258.0 

152.0 

242.5 

153.0 

240.0 

181.0 

254.5 

174.0 

251.0 

167.5 

266.0 

169.6 

264.5 

127.4 

235.0 

No.  of  meaamrements 
Corrected  growth. . . 

64.9 

202.5 

62.6 

216.5 

58.7 

236.0 

63.2 

238.0 

64.3 

269.0 

68.3 

275.0 

76.0 

258.0 

75.0 

285.5 

70.5 

304.5 

76.5 

322.5 

85.0 

370.0 

79.0 

376.0 

77.5 

344.0 

81.2 

340.5 

79.4 

378.0 

83.2 

378.5 

82.0 

380.0 

72.2 

429.0 

67.5 

372.0 

No.  of  measurements 
Corrected  growth. . . 

84.3 

337.0 

89.4 

308.0 

96.4 

322.0 

95.6 

335.0 

106.8 

335.0 

107.8 

366.0 

100.1 

376.5 

109.6 

388.0 

115.7 

377.0 

122.4 

372.5 

138.3 

372.5 

138.8 

422.5 

126.4 

455.5 

122.5 

431.5 

134.6 

478.0 

133.3 

519.5 

132.1 

540.5 

147.8 

526.5 

126.8 

457.5 

No.  of  measurements 
Corrected  growth . . . 

160.0 

517.5 

144.5 

506.5 

149.2 

485.5 

152.7 

513.5 

151.0 

530.0 

163.2 

552.0 

166.2 

567.5 

168.7 

547.5 

162.2 

593.5 

158.5 

624.5 

157.2 

622.5 

176.0 

648.5 

186.5 

653.6 

176.0 

713.0 

192.0 

738.0 

206.0 

795.0 

212.0 

763.5 

204.2 

829.5 

176.0 

699.0 

No.  of  measurements 
Corrected  growth . . . 

268.0 

451.5 

258.0 

448.0 

245.0 

457.5 

255.0 

466.5 

260.5 

476.0 

268.0 

467.0 

271.0 

475.5 

258.0 

613.0 

277.0 

473.5 

287.4 

482.0 

283.0 

611.0 

290.5 

485.5 

290.0 

536.5 

311.0 

549.0 

318.5 

548.5 

340.8 

558.6 

324.0 

529.0 

348.0 

615.0 

290.0 

488.5 

No.  of  measurements 
Corrected  growth . . . 

271.0 

757.5 

264.0 

762.5 

266.6 

791.0 

471.0 

806.5 

274.0 

790.6 

266.0 

834.5 

264.0 

804.5 

280.0 

840.0 

256.0 

818.0 

257.0 

840.0 

268.5 

899.5 

251.6 

899.5 

274.0 

866.5 

277.0 

903.5 

272.6 

959.5 

274.0 

1000.5 

257.0 

979.5 

246.0 

1004.5 

231.0 

942.5 

No.  of  measurements 
Corrected  growth . . . 

495.0 

576.5 

495.0 

676.5 

511.0 

585.5 

518.6 

671.6 

505.0 

679.5 

527.6 

651.5 

504.0 

646.0 

521.0 

661.0 

502.0 

640.0 

512.0 

663-0 

540.0 

747.5 

536.0 

726.5 

512.0 

692.0 

527.0 

701.5 

553.0 

712.0 

568.0 

721.5 

550.0 

715.0 

556.0 

704.5 

460.0 

672.0 

No.  of  measurements 
Corrected  growth . . . 
13.  Total  erowth . 

400.0 

415.5 

398.0 

422.5 

402.0 

417.0 

460.0 

422.5 

463.0 

425.0 

440.0 

426.5 

435.6 

418.5 

443.0 

438.0 

426.0 

423.5 

440.0 

455.5 

493.0 

438.5 

479.0 

511.0 

452.0 

482.0 

455.0 

441.5 

458.0 

457.0 

460.0 

502.0 

451.0 

452.0 

440.0 

476.0 

414.0 
443  0 

No.  of  measurements 
Corrected  growth. . . 

308.0 

452.5 

312.0 

455.5 

306.0 

446.0 

309.0 

459.0 

309.6 

466.5 

309.6 

483.0 

302.0 

477.5 

315.0 

464.0 

303.0 

469.5 

324.0 

478.0 

310.0 

466.0 

359.0 

496.0 

337.0 

486.5 

309.0 

490.0 

318.0 

637.0 

348.0 

537.5 

312.0 

502.0 

327’.6 

494.0 

303.0 

479.0 

No.  of  measurements 
Corrected  growth . . . 

356.0 

354.0 

358.0 

358.5 

350.0 

360.0 

359.0 

363.0 

363.0 

387.0 

374.0 

382.5 

368.0 

385.5 

356.0 

377.5 

358.0 

393.5 

363.0 

372.5 

390.0 

391.0 

373.0 

401.0 

364.0 

424.5 

365.0 

407.0 

398.0 

416.5 

396.0 

417.5 

368.0 

409.0 

362.0 

406.0 

349.0 

415.0 

No.  of  measurements 
Corrected  growth. . . 

294.0 

256.5 

296i.0 

266.0 

297.0 

249.5 

298.0 

257.5 

316.0 

249.0 

312.0 

257.0 

314.0 

257.0 

306.0 

241.0 

318.0 

258.0 

.300.0 

257.0 

314.0 

266.0 

321.0 

260.5 

338.0 

267.5 

323.0 

286.5 

329.0 

290.5 

329.0 

280.0 

321.0 

293.0 

317.0 

262.5 

322.0 

258.5 

No.  of  measurements 
Corrected  growth. . . 

225.0 

314.5 

228.5 

293.5 

214.0 

288.5 

220.0 

287.0 

212.5 

317.0 

219.0 

324.0 

218.0 

319.0 

204.0 

332.6 

218.0 

353.0 

217.0 

348.5 

223.0 

326.0 

218.0 

339.0 

224.0 

349.0 

239.0 

364.0 

242.0 

388.0 

232.0 

371.0 

242.0 

345.5 

216,5 

346.0 

212.5 

321.0 

No.  of  measurements 
Corrected  growth. . . 

280.0 

196.0 

260.0 

197.0 

256.0 

202.0 

254.0 

198.5 

280.0 

205.0 

286.0 

209.5 

281.0 

205.5 

292.5 

218.0 

311.0 

210.0 

306.0 

216.0 

286.0 

215.5 

297.0 

224.0 

306.0 

224.0 

318.0 

215.0 

338.0 

225.0 

322.5 

231.0 

306.0 

219.0 

300.0 

217.5 

277.0 

206.0 

No.  of  measurements 
Corrected  growth. . . 

179.0 

200.5 

180.0 

191.0 

184.0 

209.5 

181.0 

196.0 

187.0 

266.5 

190.0 

227.5 

186.5 

237.5 

198.0 

237.0 

190.0 

227.5 

195.5 

224.0 

195.0 

228.5 

202.0 

246.5 

202.0 

229.0 

194.0 

249.5 

204.0 

227.0 

209.5 

239.5 

198.5 

224.0 

197.0 

228.0 

187.0 

213.5 

No.  of  measurements 
Corrected  growth. . . 
20.  Total  growth . 

190.0 

349.0 

180.5 

346.5 

197.5 

359.5 

185.0 

362.0 

251.0 

367.5 

213.5 

382.0 

223.0 

378.0 

222.5 

376.0 

213.0 

394.0 

210.0 

384.0 

214.0 

370.5 

229.0 

374.0 

215.0 

384.0 

232.0 

392.0 

210.5 

396.0 

222.5 

399.5 

208.0 

386.0 

211.5 

373.5 

198.0 

355.0 

No.  of  measurements 
Corrected  growth. . . 

340.0 

119.5 

337.0 

123.0 

350.0 

129.0 

352.0 

133.0 

356.0 

135.5 

370.0 

132.0 

366.0 

130.5 

364.0 

143.0 

380.0 

162.6 

369.0 

138.0 

356.0 

139.0 

359.0 

134.0 

369.0 

130.5 

376.0 

112.5 

379.0 

114.5 

382.0 

126.5 

369.0 

114.5 

357.0 

112.5 

339.0 

117.5 

No.  of  measurements 
Corrected  growth . . . 

120.0 

150.0 

123.0 

148.5 

129.0 

147.0 

133.0 

149.0 

135.5 

156.5 

132.0 

152.0 

130.0 

149.0 

142.5 

148.0 

152.0 

154.5 

137.0 

161.0 

137.5 

167.5 

132.5 

169.5 

128.5 

174.0 

lid.5 

184.0 

112.5 

182.5 

124.0 

178.0 

112.0 

173.5 

110.0 

104.5 

115.0 

157.5 

No.  of  measurements 
Corrected  growth. . . 

156.0 

66.5 

154.0 

69.5 

152.0 

72.5 

154.0 

76.5 

161.5 

84.5 

157.0 
89  5 

154.0 

88.0 

153.0 

95.0 

160.0 

97.0 

166.0 

88.0 

172.5 

93.5 

174.5 

94.5 

179.0 

102.5 

189.0 

107.5 

187.0 

118.0 

182.5 

113.0 

177.0 

97.5 

167.5 

86.5 

160.5 

78.5 

No.  of  measurements 
Corrected  growth. . . 

71.5 

12.5 

74.5 

12.0 

77.5 

10.5 

82.0 

10.6 

90.2 

12.5 

95.5 

11.0 

93.5 

12.5 

101.0 

14.0 

103,0 

13.5 

93.3 

12.5 

99.0 

13.5 

100.0 

12.5 

108.0 

14.0 

103.5 

10.0 

124.5 

10.0 

119.0 

11.5 

102.0 

12.0 

90.5 

11.0 

82.0 

11.5 

No.  of  measurements 
Corrected  growth . . . 

13.7 

31.5 

1.3.1 

29.5 

11.5 

25.0 

11.5 

29.5 

13.6 

25.0 

12.0 

25.5 

13.6 

25.0 

15.3 

35.0 

14.7 

30.0 

13.6 

29.0 

14.6 

27.0 

13.5 

30.5 

15.1 

29.0 

10.8 

31.5 

10.8 

37.0 

12.4 

34.5 

12.9 

37.0 

11.9 

34.5 

12.4 

38.0 

No.  of  measurements 
Corrected  growth _ 

35.5 

32.5 

33.2 

37.0 

28.1 

35.5 

33.1 

36.0 

28.0 

40.0 

28.5 

39.0 

28.0 

46.0 

39.0 

39.0 

33.5 

34.0 

32.2 

34.5 

30.0 

37.5 

33.8 

33.5 

32.0 

32.0 

34.9 

32.5 

39.9 

34.0 

38.1 

33.0 

39.8 

35,0 

38.0 

37.5 

41.7 

35.5 

No.  of  measurements 
Corrected  growth. . . 

37.8 

14.0 

42.9 

14.5 

41.1 

15.0 

41.6 

14.5 

46.2 

13.5 

45.0 

12.5 

53.1 

14.0 

44.8 

14.5 

39.1 

12.0 

39.8 

13.5 

43.0 

14.0 

38.4 

14.0 

36.6 

16.0 

37.2 

12,0 

38.8 

14.0 

37.6 

13.5 

39,8 

15.5 

42.7 

14.5 

40.3 

16.0 

No.  of  measurements 
Corrected  growth. . . 

r  2S  Total  growth . 

s  &  No.  of  meas’ments 
L29.  Corrected  growth. 

16.5 

5.0 

17.1 

5.0 

17.6 

4.5 

17.0 

4.5 

15.8 

6.0 

14.6 

7.0 

.  16.3 
7.0 

16.9 

7.0 

14.0 

7.0 

15.7 

6.5 

16.2 

7.5 

16.2 

7.5 

18.5 

8.5 

13.9 

9.0 

16.2 

12.0 

15.6 

12.0 

17.9 

15.0 

16.7 

12.0 

18.4 

11.5 

6.0 

6.5 

6.0 

7.5 

5.4 

8.0 

5.4 

6.5 

7.2 

7.0 

8.4 

7.0 

8.4 

7.0 

8.4 

8.0 

8.4 

5.5 

7.8 

7.5 

9.0 

9.0 

9.0 

7.5 

10.2 

10.0 

10.8 

13.0 

14.4 

13.5 

14.4 

10.0 

18.0 

10.0 

14.3 

14.0 

13.7 

12.0 

No.  of  measurements 
Corrected  growth. . . 

T’.S 

11.5 

9.0 

13.5 

9.6 

14.5 

7.8 

14.5 

8.4 

12.0 

8.4 

14.0 

8.4 

14.0 

9.6 

13.0 

6.6 

14.0 

9.0 

10.5 

10.8 

15.0 

9.0 

16.0 

12.0 

14.5 

15.6 

21.0 

16.2 

18.5 

12.0 

17.5 

12.0 

15.5 

16.7 

13.6 

14.3 

11.0 

No.  of  measurements 
Corrected  growth. . . 

13.8 

16.2 

17.4 

17.4 

14.4 

16.8 

16.8 

15.6 

16.8 

12.6 

18.0 

19.2 

17.4 

26.2 

22.2 

21.0 

18.6 

16.2 

13.2 

314 


Table  F. — Growth  of  Sequoia  washing toniana  by  Groups  for  each  Decade — Continued, 


Group. 

1290- 

1300  A.D. 

o 

f 

00 

(M 

1271-80  , 

o 

O 

M 

1 

1251-60 

1241-50  j 

S 

1 

1221-30  j 

1211-20 

Ol-lOZt 

2 

06-1811 

1171-80 

1161-70 

1151-60 

1141-50 

•>« 

wH 

1121-30 

1110-20 

e 

1 

o 

445.5 
19 

117.6 

235.5 
10 

70.8 
401.0 

17 

135.0 

441.0 

26 

167.5 
632.0 

42 

258.8 

495.0 

42 

231.0 

873.0 

75 

472.0 

663.0 

59 

405.0 

445.5 
49 

303.0 

510.5 
51 

370.0 

392.5 
47 

.302.5 

244.5 
33 

200.0 

319.0 

47 

273.0 

205.0 

30 

185.5 

211.5 
25 

196.0 

361.5 
49 

344.0 

126.5 
17 

12.3.5 
161.0 

24 

164.0 

67.0 

11 

70.0 

10.0 

2 

10.8 
34.0 

4 

37.3 

37.0 

5 

41.9 
13.0 

2 

14.9 
7.5 

1 

8.9 

9.0 

1 

10.6 

18.5 

2 

22.2 

357.5 
19 
92.3 

226.5 

319.5 
16 
82.5 

222.5 

339.0 

14 

87.5 

233.0 

307.0 

14 

77.4 

225.5 

258.5 
11 
65.2 

210.5 

249.5 

11 

61.4 

198.0 

265.0 

9 

62.5 

240.0 

10 

67.0 

340.5 

167.5 
6 

39.5 

236.0 

9 

65.8 

387.5 

36.5 

2 

8.6 

237.0 

9 

65.0 

360.5 

31.5 

2 

7.1 

267.0 

9 

71.8 

366.5 

No.  of  measurements 
Corrected  growth . . . 

214.5 
9 

56.8 

349.5 

209.0 

8 

54.0 

377.5 

196.5 
8 

49.5 

445.5 
17 

131.3 

471.5 

231.5 
8 

57.0 

384.0 

15 

112.0 

456.5 

250.5 
8 

59.0 

357.5 
15 

103.2 

507.5 

233.0 

6 

53.7 

369.0 

15 

105.5 

532.5 

97.5 

No.  of  measurements 
Corrected  growth . . . 

3 

22.0 

394.0 

15 

111.5 

558.0 

67.5 

367.0 

66.5 

338.5 

68.0 

309.5 

65.2 

308.0 

60.2 

309.5 

56.0 

304.0 

400.5 
15 

111.6 
604.0 

408.5 

15 

111.8 

616.0 

No.  of  measurements 
Corrected  growth. .  . 

122.0 

430.0 

111.8 

421.0 

100.8 

457.0 

99.5 

437.0 

98.8 

440.0 

97.0 

465.0 

107.7 

473.0 

121.3 

496.5 

110.7 

490.8 

111.3 

454.5 

105.0 

469.5 

112.5 

474.5 

No.  of  measurements 
Corrected  growth . . . 

162.0 

664.5 

157.5 

680.0 

169.0 

619.0 

159.3 

655.5 

158.2 

700.5 

165.4 

712.5 

166.5 

810.0 

172.5 

746.0 

168.5 

767.5 

153.0 

709.0 

1.56.1 

734.0 

156.7 

756.5 

153.6 

716.0 

141.3 

697.0 

162.0 

751.0 

168.3 

783.5 

175.0 

845.0 

189.0 

913.5 

191.0 

879.5 

No.  of  measurements 
Corrected  growth . . . 

268.0 

479.0 

271.0 

519.0 

244.0 

543.5 

255.2 

547.5 

270.4 

588.^5 

272.2 

562.5 

307.1 

585.5 

280.5 

620.0 

284.6 

596.0 

260.0 

567.0 

267.7 

565.5 

270.5 

573.5 

253.5 

588.5 

244.0 

614.0 

260.0 

645.5 

268.7 

697.5 

286.2 

706.5 

305.6 

730.5 

291.7 

692.0 

No.  of  measurements 
Corrected  growth . . . 

220.0 

879.5 

2.36.0 

858.0 

246.5 

874.5 

243.0 

880.5 

257.0 

904.0 

243.0 

967.0 

251.0 

968.5 

263.0 

992.0 

250.0 

927.0 

237.0 

945.0 

23^0 

957.5 

231.5 

990.5 

235.0 

959.0 

242.0 

988.0 

250.5 

lOOO.O 

269.0 

1085.5 

270.0 

1112.5 

277.0 

1115.2 

260.0 

1147.5 

No.  of  measurements 
Corrected  growth . .  . 

468.0 

686.0 

451.0 

694.5 

453.0 

737.0 

450.0 

755.5 

455.0 

730.0 

480.0 

744.0 

475.0 

748.5 

480.0 

707.5 

443.0 

783.5 

445.0 

797.0 

445.0 

796.5 

455.0 

798.0 

435.0 

783.0 

44.5.0 

709.0 

442.0 

782.0 

473.0 

818.5 

482.0 

810.5 

478.0 

824.5 

486.0 

848.0 

No.  of  measurements 
Corrected  growth. . . 

415.0 

461.0 

416.0 

463.5 

4.37.0 

478.0 

443.0 

463.5 

421.0 

452.5 

424.0 

442.0 

422.0 

458.0 

393.0 

446.5 

455.0 

458.0 

431.0 

459.5 

425.0 

433.0 

420.0 

502.0 

407.0 

486.5 

393.0 

459.5 

395.0 

481.0 

409.0 

524.0 

398.0 

522.0 

400.0 

522.0 

406.0 

520.0 

No.  of  measurements 
Corrected  growth . . . 

311.0 

509.0 

312.0 

516.0 

320.0 

520.0 

308.0 

507.5 

301.0 

516.0 

292.0 

493.5 

300.6 

522.0 

290.0 

502.5 

293.0 

532.0 

291.0 

567.5 

272.0 

515.0 

312.0 

529.5 

298.0 

506.5 

280.0 

509.5 

290.0 

506.0 

311.0 

532.0 

306.0 

553.0 

302.0 

565.5 

297.0 

548.0 

No.  of  measurements 
Corrected  growth. . . 

367.0 

387.5 

371.0 

371.0 

372.0 

384.0 

362.0 

399.0 

367.0 

389.0 

349.0 

386.0 

365.0 

418.5 

350.0 

381.5 

368.0 

407.0 

391.0 

405.0 

353.0 

374.0 

360.0 

368.5 

343.0 

385.5 

343.0 

392.5 

338.0 

395.5 

352.0 

393.0 

362.0 

399.0 

367.0 

412.5 

352.0 

414.5 

No.  of  measurements 
Corrected  growth . . . 

16.  Total  growth . 

No.  of  measurements 
Corrected  growth . .  . 

298.0 

245.0 

283.5 

232.5 

292.0 

249.5 

302.0 

25-5.5 

293.0 

257.5 

290.0 

258.5 

312.0 

261.0 

284.0 

261.5 

302.0 

262.0 

299.0 

270.0 

274.5 

265.0 

270.0 

263.0 

281.0 

255.5 

285.0 

256.0 

286.0 

265.0 

283.0 

275.0 

286.0 

289.0 

294.5 

278.5 

294.0 

272.0 

200.0 

330.0 

189.0 

334.5 

202.0 

323.0 

206.0 

332.0 

206.5 

328.5 

206.5 

339.5 

207.0 

361.0 

206.5 

343.0 

206.0 

345.0 

211.0 

351.0 

206.0 

347.0 

203.5 

364.0 

197.0 

343.5 

196.0 

339.5 

202.5 

338.5 

209.0 

348.0 

218.5 

345.0 

210.0 

322.0 

205.0 

348.5 

No.  of  measurements 
Corrected  growth. . . 

283.0 

208.5 

286.0 

225.0 

275.0 

227.5 

282.0 

229.0 

279.0 

230.0 

288.0 

230.5 

305.0 

221.5 

289.0 

221.0 

289.0 

222.5 

294.0 

250.0 

280.0 

208.5 

303.0 

213.0 

284.0 

209.5 

280.0 

209.5 

278.0 

218.0 

284.0 

221.5 

280.0 

229.5 

260.0 

224.0 

281.0 

222.0 

No.  of  measurements 
Corrected  growth . . . 

188.0 

199.0 

203.0 

205.0 

205.0 

211.0 

204.0 

204.5 

204.0 

199.0 

204.0 

201.5 

197.0 

198.0 

196.5 

201.0 

198.0 

195.5 

219.0 

205.0 

181.0 

205.0 

185.0 

204.0 

181.5 

203.5 

181.0 

212.0 

188.0 

217.5 

191.0 

187.5 

197.0 

197.0 

191.0 

195.0 

189.0 

198.0 

No.  of  measurements 
Corrected  growth. . . 

20.  Total  growth . 

No.  of  measurements 
Corrected  growth. . . 

184.0 

361.5 

190.0 

375.0 

195.0 

361.5 

189.0 

381.0 

183.5 

382.5 

185.0 

378.0 

181.5 

389.0 

184.5 

374.0 

179.0 

371.0 

187.5 

341.0 

157.5 

355.5 

186.5 

343.0 

186.0 

350.5 

193.0 

361.5 

198.6 

367.5 

171.0 

368.0 

179.0 

395.5 

177.0 

382.0 

179.0 

370.0 

344.0 

125.5 

356.0 

116.0 

343.0 

115.0 

361.0 

112.5 

362.0 

117.0 

358,0 

121.0 

368.0 

124.0 

353.0 

133.5 

350.0 

137.5 

321.0 

138.0 

334.0 

135.0 

322.0 

133.0 

3260 

135.5 

339.0 

119.0 

343.0 

124.5 

343.0 

122.5 

368.0 

126.0 

355.0 

124.0 

344.0 

119.0 

No.  of  measurements 
Corrected  growth . . . 

122.5 

159.5 

113.0 

166.5 

112.0 

172.0 

109.5 

168.5 

113.5 

172.0 

117.0 

160.5 

120.0 

171.0 

129.0 

179.0 

133.0 

173.0 

133.5 

175.0 

130.0 

162.0 

128.0 
160  5 

130.5 

148.0 

114.5 

157.0 

119.5 

156.0 

122.5 

162.0 

120.5 

177.5 

118.5 

188.5 

114.0 

186.6 

No.  of  measurements 
Corrected  growth . . . 

162.0 

73.0 

169.0 

73.0 

174.0 

75.0 

170.5 

87.0 

173.5 

93.0 

162.0 

95.5 

172.5 

92.5 

180.0 

83.0 

174.0 

75.5 

175.5 

79.5 

162.5 

79.0 

161.0 

85.0 

148.0 

78.5 

157.0 

77.5 

156.0 

80.0 

162.0 

97.0 

177.5 

70.5 

188.0 

71.5 

186.0 

74.5 

No.  of  measurement.^ 
Corrected  growth. . . 

76.3 

13.5 

76.2 

14.5 

78.0 

12.5 

90.2 

11.5 

96.5 

12.0 

99.0 

14.0 

96.0 

13.5 

86.0 

13.5 

78.0 

13.5 

82.0 

11.0 

81.5 

11.5 

88.0 

14.0 

81.0 

10.0 

80.0 

11.5 

82.0 

10.5 

99.5 

15.5 

72.0 

16.0 

73.0 

14.5 

77.0 

15.0 

No.  of  measurements 
Corrected  growth . . . 

14.4 

28.0 

15.5 

26.0 

13.3 

33.5 

12.3 

37.5 

12.8 

33.0 

14.9 

34.5 

14.3 

36.0 

14.3 

33.5 

14.3 

29.5 

11.6 

29.0 

12.1 

27.0 

14.7 

23.5 

10.5 

29.0 

12.1 

29.0 

11.0 

32.0 

16.2 

30.0 

16.7 

27.0 

15.2 

21.5 

15.7 

24.5 

No.  of  measurements 
Corrected  growth . . . 

30.6 

39.0 

28.4 

39.5 

36.7 

47.5 

41.0 

36.0 

36.1 

34.5 

37.6 

31.5 

39.3 

32.0 

36,4 

28.0 

32.2 

36.5 

31.6 

33,0 

31.5 

35.5 

25.4 

33.0 

31.2 

34.0 

31.2 

36.0 

34.4 

30.0 

32.1 

30.5 

28.9 

29.5 

23.1 

34.5 

26.2 

31.5 

No.  of  measurements 
Corrected  growth . . . 

44.0 

13.5 

44.6 

16.0 

53.5 

13.5 

40.6 

11.5 

38.8 

15.0 

35.4 

12.0 

36.0 

15.0 

31.4 

14.5 

40.8 

14.0 

36.9 

12.5 

39.7 

16.0 

36.8 

13.5 

37.9 

17.0 

40.1 

14.5 

33.3 

16.0 

33.8 

15.0 

32.7 

14.5 

38.2 

14.5 

34.8 

14.5 

No.  of  measurements 
Corrected  growth. . . 

(  28  Total  growth . 

<  &  No.  of  meas’ments 
(  29.  Corrected  growth . 

15.5 

6.5 

18.3 

6.0 

15.4 

4.5 

13.1 

6.0 

17.1 

5.5 

13.6 

5.0 

17.0 

5.5 

16.5 

6.0 

15.9 

4.0 

14.1 

4.5 

18.1 

4.5 

15.2 
4  5 

19.2 

4.0 

16.3 

5.0 

18.0 

5.0 

16.9 

5.0 

16.2 

6.0 

16.2 

6.0 

16.2 

5.5 

7.7 

9.0 

7.1 

10.0 

5.3 

14.0 

7.1 

13.0 

6.5 

17.0 

5.9 

13.0 

6.5 

12.0 

7.0 

14.5 

4.7 

12.5 

5.3 

18,0 

5.3 

16.0 

5.3 

14.0 

4.7 

12.5 

5.8 

10.5 

5.8 

13.0 

5.8 

9.0 

7.0 

9.0 

6.9 

12.0 

6.4 

11.0 

No.  of  measurements 
Corrected  growth. . . 

10.6 

15.5 

11.8 

16.0 

16.5 

11.5 

15.3 

11.0 

20.0 

10.5 

15.3 

8.0 

14.1 

8.0 

17.0 

9.0 

1.46 

8.0 

21.0 

7.5 

18.7 

10.5 

16.3 

7.5 

14.5 

7.0 

12.2 

7.0 

15.1 

5.5 

10.4 

6.0 

10.4 

7.5 

13.9 

8.0 

12.7 

8.5 

No.  of  measurements 
Corrected  growth . . . 

18.6 

19.2 

13.8 

13.2 

12.6 

9.6 

9.6 

10.8 

9.6 

9.0 

12.5 

8.9 

8.3 

8.3 

6.5 

7.1 

8.9 

9.4 

10.0 

Table  F. — Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade — Continued.  315 


Group. 

1091-  1 

IIOOA.D.  1 

1081-90 

1071-80 

1061-70 

1051-60 

1041-50 

1031-40 

1021-30 

1011-20 

o 

1 

o 

o 

991- 

1000  - 

981-90 

971-80 

961-70 

? 

m 

941-SO  I 

931-40  1 

921-30 

o 

1 

o> 

901-10 

398.0 

15 

107.0 

604.5 
26 

185.7 

960.0 

42 

314.5 
790.0 

42 

293.0 

1114.1 

75 

468.0 

833.0 

59 

393.0 

536.0 

49 

302.0 

553.0 

51 

352.0 

404.0 

47 

285.0 

293.0 

33 

219.0 

332.0 

47 

266.0 

238.0 

30 

202.0 

204.5 
25 

185.0 

365.0 

49 

339.0 

125.5 
17 

120.0 

197.5 
24 

196.5 
73.0 
11 
74.0 
15.0 

2 

1.5.7 

23.5 

4 

25.2 

28.0 

5 

30.9 

13.5 
2 

1.5.1 

5.5 

1 

6.4 
10.0 

1 

11.5 

8.5 
2 

10.0 

461.5 
15 

121.8 

606.5 

428.0 

16 

110.6 

615.5 

398.5 
14 

100.6 
567.6 

287.0 

11 

72.2 

572.0 

297.5 
11 
73.2 

577.5 

240.5 
9 

59.2 

567.5 

189.5 

7 

44.7 

614.0 

157.0 

5 

37.1 

649.0 

91.0 

3 

20.6 

659.5 

No.  of  measurements 
Corrected  growth . . . 

624.5 

26 

171.0 

1142.5 

607.5 

26 

163.4 

929.5 

549.5 

26 

145.0 

921.0 

485.0 

22 

125.1 

791.5 

491.0 

22 

124.0 

797.5 

42 

226.4 

1021.5 

493.5 
21 

121.5 
764.0 

40 

216.8 

965.5 

462  5 
17 

113.8 

726.5 
40 

203.5 
1038.5 

346.0 

14 

81.6 

762.5 
40 

209.5 
1086.5 

173.0 

8 

40.8 

723.0 

40 

195.2 

1180.5 

97.5 
4 

22.5 
628.0 

40 

167.0 

1182.5 

No.  of  measurements 
Corrected  growth _ 

184.8 

992.0 

185.5 

882.0 

169.1 

907.5 

168.5 

1011.0 

168.5 

909.6 

164.0 

920.0 

175.8 

1022.5 

183.8 

1039.5 

184.0 

1126.5 

No.  of  measurements 
Corrected  growth. . . 

322.0 

746.0 

283.0 

775.0 

288.6 

763.5 

318.0 

789.5 

284.0 

908.5 

284.5 

929.5 

313.0 

972.0 

313.8 

1023.0 

336.0 

1063.5 

338.0 

965.5 

272.2 

1056.5 

267.0 

991.0 

227.0 

1011.0 

No.  of  measurements 
Corrected  growth . . . 

374.0 

1167.5 

381.0 

1176.6 

273.0 

1200.5 

279.0 

1244.0 

318.0 

1330.0 

321.5 

1394.0 

333.5 

1523.5 

347.0 

1634.5 

356.0 

1727.0 

320.5 

1555.0 

^6.0 

1436.5 

321.0 

1393.0 

324.5 

1439.0 

325.0 

1515.0 

304.0 

1528.5 

324.0 

1000.5 

336.0 

1678.5 

361.0 

1613.0 

357.0 

1734.0 

No.  of  measurements 
Corrected  growth . . . 

484.0 

871.5 

482.0 

836.5 

486.0 

845.0 

497.0 

845.0 

524.0 

868.5 

545.0 

893.0 

590.0 

974.6 

590.0 

1011.0 

658.0 

1004.5 

584.0 

969.0 

534.0 

909.0 

512.0 

931.0 

522.0 

958.5 

545.0 

994.0 

541.0 

1008.5 

560.0 

988.5 

582.0 

1011.0 

553.0 

1116.5 

588.0 

1181.0 

59 

452.0 

729.0 

No.  of  measurements 
Corrected  growth . . . 

408.0 

637.0 

385.0 

665.0 

386.0 

535.5 

380.0 

568.0 

386.0 

592.0 

392.0 

622.0 

425.0 

650.0 

436.0 

661.5 

444.0 

686.5 

408.0 

662.5 

378.0 

608.5 

382.0 

618.0 

388.0 

609.0 

398.0 

629.0 

402.0 

625.0 

389.0 

667.0 

395.0 

702.5 

433.0 

723.0 

No.  of  measurements 
Corrected  growth . . . 

298.0 

581.5 

310.0 

575.0 

290.0 

531.0 

303.0 

532.5 

312.0 

594.0 

323.0 

592.0 

334.0 

617.6 

336.6 

685.0 

343.0 

646.0 

326.0 

622.0 

296.0 

614.5 

296.0 

621.0 

288.0 

610.5 

295.0 

619.0 

289.0 

621.5 

304.0 

619.0 

317.0 

634.5 

323.0 

685.5 

321.0 

682.0 

No.  of  measiirements 
Corrected  growth . . . 

366.0 

395.0 

358.0 

417.5 

327.0 

408.0 

325.0 

440.0 

356.0 

427.6 

350.0 

429.5 

362.0 

445A 

394.0 
468  5 

368.0 

472.0 

349.0 

456.5 

339.0 

458.0 

339.0 

445.0 

329.0 

418.0 

329.0 

407.5 

327.0 

431.5 

322.0 

454.5 

324.0 

480.5 

345.0 

502.0 

341.0 

501.5 

No.  of  measurements 
Corrected  growth _ 

277.0 

289.5 

292.0 

312.0 

284.0 

304.0 

304.0 

288.0 

293.0 

294.0 

292.0 

320.0 

300.0 

318.5 

312.0 

320.5 

312.0 

321.0 

299.0 

319.5 

297.0 

300.5 

285.0 

326.5 

265.5 

307.0 

256.0 

306.0 

268.0 

317.5 

278.0 

329.0 

290.0 

334.5 

290.5 

327.0 

295.0 

343.5 

No.  of  measurements 
Corrected  growth . . . 

216.0 

353.5 

231.5 

348.0 

225.0 

331.5 

212.0 

353.0 

215.0 

375.5 

233.5 

378.5 

231.0 

403.0 

231.0 

419.5 

230.0 

392.5 

228.0 

420.5 

213.0 

377.0 

230.0 

386.0 

215.0 

391.5 

213.0 

391.5 

219.0 

380.5 

224.5 

367.5 

226.0 

390.0 

218.5 

390.5 

227.0 

381.5 

No.  of  measurements 
Corrected  growth . . . 

281.0 

208.0 

276.0 

206.0 

262.0 

211.0 

277.0 

214.0 

293.6 

250.0 

294.0 

254.0 

312.0 

257.6 

322.0 

244.0 

302.0 

259.5 

322.0 

262.5 

288.0 

226.0 

293.0 

234.0 

296.0 

243.0 

295.0 

250.5 

286.0 

245.5 

275.0 

270.0 

291.0 

262.5 

289.0 

272.0 

282.0 

249.0 

No.  of  measurements 
Corrected  growth. . . 

174.5 

208.0 

173.0 

216.0 

177.0 

207.0 

179.0 

212.0 

207.0 

197.5 

210.0 

209.5 

213.0 

201.5 

200.0 

204.0 

215.5 

217.0 

213.5 

209.0 

181.0 

219.0 

188.0 

224.5 

193.0 

210.0 

199.5 

209.5 

195.0 

195.5 

214.0 

202.0 

207.0 

204.5 

214.0 

206.0 

195.0 

215.5 

No.  of  measurements 
-Corrected  growth. . . 

187.0 

358.0 

194.0 

362.0 

185.0 

393.5 

189.0 

397.0 

176.0 

411.0 

185.5 

420.0 

178.0 

435.0 

180.0 

419.5 

191.0 

411.0 

183.0 

386.5 

191.0 

410.5 

195.0 

398.0 

182.0 

392.0 

181.0 

383.5 

168.0 

390.0 

173.0 

384.0 

174.0 

395.0 

175.0 

396.0 

182.5 

405.0 

No.  of  measurements 
Corrected  growth. . . 

333.0 

130.0 

336.0 

129.0 

365.0 

121.5 

367.0 

125.0 

380.0 

131.5 

387.0 

141.0 

417.0 

138.0 

384.0 

130.5 

376.0 

125.0 

353.0 

118.0 

373.0 

125.5 

361.0 

113.5 

354.0 

122.5 

346.0 

117.5 

350.0 

119.0 

344.0 

116.5 

352.0 

125.0 

352.0 

125.5 

358.0 

132.0 

No.  of  measurements 
Corrected  growth . . . 

124.0 

182.5 

123.0 

185.5 

115.5 

176.5 

119.0 

179.0 

125.0 

177.0 

134.0 

138.5 

131.6 

199.0 

124.0 

187.5 

118.0 

184.0 

112.0 

177.5 

118.5 

178.5 

107.0 

159.5 

115.0 

162.5 

110.5 

158.0 

111.0 

155.5 

109.0 

171.0 

116.5 

170.0 

117.0 

179.0 

122.5 

165.0 

No.  of  measurements 
Corrected  growth . . . 

181.0 

72.0 

184.0 

81.0 

174.5 

82.0 

177.0 

78.5 

174.5 

81.5 

185.5 

80.5 

195.5 

89.0 

184.0 

97.5 

180.5 

97.5 

174.0 

71.0 

175.0 

70.0 

155.5 

65.5 

158.5 

72.5 

154.0 

68.5 

151.0 

62.5 

166.5 

66.5 

165.5 

66.5 

174.0 

67.5 

160.0 

67.5 

No.  of  measurements 
Corrected  growth. . . 

73.0 

13.0 

82.0 

13.0 

83.0 

15.0 

79.5 

13.0 

82.5 

15.5 

81.5 

18.5 

90.0 

16.5 

98.0 

15.0 

.  98.0 
14.5 

71.0 

11.5 

70.0 

11.5 

65.5 

13.0 

72.5 

12.5 

68.5 

11.5 

62.5 

12.0 

66.5 

13.5 

66.5 

12.5 

87.5 

12.5 

67.5 

11.5 

No.  of  measurements 

Corrected  growth _ 

25.  Total  growth. .  ^. . . . 
No.  of  measurements 
Corrected  growth. . . 

13.6 

26.0 

13.6 

23.5 

15.6 

24.0 

13.5 

27.5 

16.1 

28.0 

19.1 

28.0 

17.0 

32.0 

15.5 

27.0 

15.0 

25.0 

12.0 

28.5 

11.9 

29.5 

13.4 

24.5 

12.9 

23.5 

ii.9 

29.0 

12.4 

24.5 

13.9 

22.5 

12.8 

29.5 

12.8 

29.0 

11.8 

30.0 

27.7 

31.0 

2.5.1 

33.5 

25.6 

31.5 

29.1 

34.5 

29.6 

40.0 

29.6 

37.5 

33.8 

32.5 

28.6 

28.5 

26.4 

26.5 

29.2 

32.5 

31.2 

29.5 

26.8 

31.0 

25.0 

30.0 

30.5 

30.0 

25.2 

30.0 

23.6 

29.5 

30.9 

31.5 

30.3 

29.0 

31.3 

26.0 

No.  of  measurements 
Corrected  growth. . . 

34.1 
■  13.0 

36.8 

17.0 

34.6 

17.5 

37.9 

19.5 

43.8 

17.5 

41.0 

19.0 

35.6 

17.5 

31.1 

19.5 

28.9 

18.5 

35.4 

14.0 

32.1 

12.0 

33.7 

11.5 

32.5 

13.0 

32.5 

12.5 

32.5 

11.5 

31.9 

14.0 

34.0 

15.5 

31.2 

18.5 

28.0 

17.0 

No.  of  measurements 
Corrected  growth. . . 

r  28  Total  growth . 

<  &  No.  of  meas’ments 
1.  29.  Corrected  growth . 

14.5 

6.0 

19.0 

7.0 

19.5 

8.0 

21.6 

8.0 

19.4 

10.0 

21.1 

7.0 

19.4 

10.0 

21.6 

10.0 

20.4 

10.0 

15.4 

0.5 

13.2 

10.0 

12.6 

9.5 

14.3 

9.5 

13.7 

6.5 

12.6 

4.5 

15.3 

3.5 

16.1 

3.5 

20.2 

3.5 

18.5 

3.0 

6.9 

10.0 

8.1 

14.0 

9.2 

14.0 

9.2 

14.0 

11.5 

21.0 

8.0 

21.0 

11.4 

16.0 

11.4 

18.0 

11.4 

16.0 

10.8 

13.0 

11.4 

11.0 

10.8 

12.0 

10.8 

12.5 

7.4 

11.5 

5.1 

11.0 

4.0 

13.0 

4.0 

11.0 

3.9 

11.0 

3.4 

10.0 

No.  of  measurements 
Corrected  growth . . .- 

11.5 

9.5 

16.1 

10.0 

16.0 

12.5 

16.0 

13.5 

24.0 

12.0 

24.0 

12.5 

18.3 

13.5 

20.5 

14.0 

18.3 

12.6 

14.8 

8.0 

12.5 

8.0 

13.6 

9.5 

14.2 

8.5 

13.0 

11.0 

12.4 

8.5 

14.7 

9.0 

12.4 

12.0 

12.4 

11.0 

11.2 

11.0 

No.  of  measurements 
Corrected  growth. . . 

11.1 

11.7 

14.6 

15.7 

14.0 

14.5 

15.7 

16.2 

14.5 

9.2 

9.2 

11.0 

9.8 

12.7 

9.8 

10.3 

13.7 

12.6 

12,6 

316 


Table  F. — Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade — Continued, 


Group. 

o 

f  Q 

s  ^ 
00 

881-90 

871-80 

1 

861-70  1 

1 

o 

t 

in 

CO 

841-SO 

831-40 

821-30 

811-20 

801-10 

Ok 

i> 

781-90 

S 

1 

761-70 

751-60 

741-50 

731-40 

o 

7 

711-20 

701-10 

32.0 

2 

7.2 

746.5 
34 

198.5 

1104.5 
42 

330.0 

1763.5 
75 

593.0 

1121.5 
59 

423.0 

726.0 

49 

316.0 

709.0 

51 

348.0 

499.0 

47 

290.0 

330.5 
33 

217.0 

393.5 
47 

289.0 

257.0 

30 

200.0 

196.5 
25 

165.0 

381.0 

49 

336.0 

132.5 
17 

122.5 
166.0 

24 

161.0 

69.0 

11 

69.0 

11.5 
2 

11.8 

23.5 

4 

24.5 

25.5 

5 

27.5 
18.0 

2 

19.6 
4.0 
1, 
4.5 
8.0 
1 

9.0 

9.0 

2 

10.3 

No.  of  measurements 
Corrected  growth _ 

601.0 

31 

156.2 

1037.5 

515.0 

29 

131.0 

992.0 

469.0 

23 

120.5 

962.0 

385.0 

19 

97.6 

1017.5 

456.0 

19 

112.9 

990.0 

298.5 

14 

74.2 

1032.0 

318.0 

13 

75.4 

892.5 

289.5 

10 

65.5 

1049.5 

42.0 

2 

9.5 

976.5 

No.  of  measurements 
Corrected  growth. . . 

1079.5 
42 

280.3 

1658.5 

1096.5 
42 

279.0 

1637.5 

805.5 
24 

214.5 
1583.5 

499.5 

24 

129.7 

1486.5 

454.0 

22 

115.3 

1494.5 

439.5 
18 

110.5 
1452.0 

417.0 

18 

101.5 

1539.5 
75 

437.5 

1373.5 

277.5 

13 

65.8 

1526.5 

73 

433.0 

1455.0 

289.5 

11 

66.8 

1450.5 
73 

405.0 

1464.5 

103.5 

5 

23.4 

1464.5 

73 

402.0 

1644.0 

59 

608.0 

953.0 

No.  of  measurements 
Corrected  growth. . . 

307.0 

1774.5 

291.0 

1697.5 

279.0 

1736.0 

292.0 

1727.5 

281.0 

1727.5 

289.0 

1688.0 

246.0 

1694.5 

283.0 

1618.5 

259.6 

1666.5 

No.  of  measurements 
Corrected  growth . . . 

589.0 

1055.5 

458.0 

1055.5 

564.0 

1110.5 

456.0 

1147.5 

M9.0 

1172.5 

532.0 

1201.0 

529.0 

1180.5 

500.0 

1212.0 

510.0 

1203.0 

503.0 

1239.0 

491.0 

1253.0 

467.0 

1288.5 

437.0 

1218.5 

435.6 

1332.5 

418.0 

1417.5 

No.  of  measurements 
Corrected  growth . . . 

392.0 

763.0 

388.0 

755.0 

404.0 

731.0 

413.0 

740.0 

418.0 

754.0 

425.0 

762.5 

412.0 

766.0 

418.0 

839.5 

412.0 

821.0 

418.0 

859.5 

420.0 

828.0 

425.0 

793.5 

398.0 

778.5 

432.0 

826.5 

455.0 

809.C 

437.0 

822.0 

458.0 

831.5 

457.0 

893.5 

No.  of  measurements 
Corrected  growth . . . 

330.0 

647.5 

324.0 

651.0 

308.0 

679.0 

308.0 

678.6 

309.0 

665.5 

309.0 

693.5 

309.0 

727.0 

334.0 

717.5 

325.0 

724.0 

337.0 

752.0 

321.0 

778.5 

304.0 

746.0 

294.0 

713.5 

308.0 

798.0 

298.0 

815.5 

300.0 

812.0 

300.0 

773.5 

320.0 

809.5 

336.0 

822.0 

No.  of  measurements 
Corrected  growth. . . 

314.0 

498.0 

314.0 

503.0 

322.0 

510.5 

318.0 

506.0 

308.5 

496.5 

318.0 

497.0 

330.0 

506.0 

322.0 

474.0 

321.0 

494.0 

330.0 

510.0 

336.0 

513.5 

318.0 

525.5 

300.0 

518.0 

332.0 

579.5 

336.0 

549.0 

332.0 

531.0 

313.0 

527.0 

325.0 

540.0 

337.0 

681.0 

No.  of  measurements 
Corrected  growth . . . 

285.5 

324.5 

284.0 

3C9.0 

284.0 

301.0 

278.5 

299.0 

268.0 

325.5 

264.5 

343.0 

268.0 

328.5 

246.5 

329.5 

254.0 

328.0 

259.0 

335.5 

257.0 

333.5 

260.0 

321.0 

254.0 

336.0 

280.0 

355.0 

261.5 

354.0 

250.0 

371.0 

245.0 

369.0 

249.0 

365.5 

265.0 

379.0 

No.  of  measurements 
Corrected  grow'th . . . 

210.5 

384.5 

198.0 

352.5 

191.0 

360.0 

187.0 

370.5 

201.0 

391.0 

209.0 

390.5 

197.5 

395.5 

196.0 

405.5 

192.0 

405.0 

193.5 

407.0 

190.0 

400.0 

180.5 

397.5 

186.0 

400.5 

195.0 

411.5 

194.0 

414.0 

197.0 

434.0 

194.0 

393.0 

190.0 

401.0 

194.0 

408.5 

No.  of  measurements 
Corrected  growth. . . 

281.0 

245.5 

256.0 

241.5 

260.0 

248.0 

266.0 

247.5 

280.0 

228.5 

277.0 

248.5 

277.0 

246.1 

282.0 

246.5 

278.0 

254.5 

276.0 

258.0 

269.0 

261.0 

264.0 

254.0 

264.0 

263.5 

269.0 

270.5 

268.0 

258.5 

276.0 

252.0 

247.0 

263.5 

245.0 

267.0 

246.0 

255.0 

No.  of  measurements 
Corrected  growth. . . 

190.0 

202.5 

186.0 

191.0 

190.0 

197.5 

188.0 

197.5 

173.0 

188.0 

187.0 

192.5 

185.0 

190.5 

184.0 

193.0 

189.0 

210.5 

191.0 

212.5 

192.0 

196.5 

186.0 

205.5 

192.0 

207.0 

195.0 

207.0 

184.0 

192.5 

178.0 

194.5 

184.5 

191.5 

185.0 

182.5 

175.0 

184.0 

No.  of  measurements 
Corrected  growth . . . 

169.5 

376.0 

159.0 

399.5 

164.0 

374.0 

163.0 

392.5 

154.5 

367.5 

157.5 

382.0 

155.0 

373.5 

157.0 

378.5 

170.0 

376.0 

171.0 

392.5 

157.5 

394.0 

164.0 

398.5 

164.5 

404.5 

163.5 

417.0 

151.0 

429.5 

152.0 

399.5 

149.0 

401.6 

141.0 

386.5 

m.6 

381.5 

No.  of  measurements 
Corrected  growth . , . 

331.0 

124.0 

350.0 

121.0 

327.0 

111.5 

342.0 

109.5 

318.0 

117.0 

330.0 

112.5 

321.0 

111.0 

323.0 

127.0 

320.0 

124.5 

332.0 

122.5 

332.0 

114.0 

334.0 

111.0 

338.0 

115.0 

346.0 

119.0 

354.0 

115.5 

329.0 

114.5 

330.0 

105.5 

316.0 

108.0 

310.0 

112.0 

No.  of  measurements 
Corrected  growth . . . 

114.0 

159.0 

111.0 

164.0 

102.0 

155.5 

100.0 

159.0 

106.6 

170.0 

102.0 

166.0 

100.0 

169.0 

104.5 

176.5 

112.0 

166.5 

109.5 

169.0 

102.0 

156.5 

98.5 

149.5 

101.0 

161.0 

104.0 

160.0 

101.0 

151.5 

99.5 

164.5 

91.0 

156.5 

92.5 

154.0 

96.0 

163.0 

No.  of  measurements 
Corrected  growth . . . 

154.0 

71.5 

158.5 

68.6 

150.0 

76.5 

153.0 

78.0 

163.5 

70.5 

159.5 

71.5 

162.0 

64.5 

169.0 

73.0 

159.0 

74.5 

161.0 

78.0 

148.0 

710 

141.0 

73.0 

151.5 

69.0 

150.0 

77.0 

142.0 

76.5 

144.0 

64.0 

1^.5 

68.5 

143.0 

71.0 

150.5 

72.5 

No.  of  measurements 
Corrected  growth . . . 

71.5 

13.5 

68.0 

10.0 

76.0 

12.0 

77.2 

11.5 

69.9 

11.0 

70.8 

9.5 

63.8 

8.5 

72.1 

8.5 

73.5 

10.0 

76.9 

11.5 

70.0 

11.0 

71.8 

12.5 

67.8 

10.5 

75.5 

11.5 

73.8 

13.5 

62.5 

11.0 

66.7 

11.6 

69.0 

13.5 

70.2 

10.0 

No.  of  measurements 
Corrected  growth. . . 

13.8 

25.5 

10.2 

20.0 

12.2 

21.5 

11.7 

21.5 

11.2 

20.5 

9.6 

22.0 

8.6 

23.5 

8.6 

23.5 

10.1 

25.0 

11.6 

24.5 

11.1 

26.0 

12.5 

25.0 

10.5 

25.5 

11.5 

25.5 

13.5 

27.6 

10.9 

24.0 

11.4 

24.0 

13.4 

23.0 

9.9 

24.0 

No.  of  measurements 
Corrected  growth. . . 

26.5 

29.0 

20.8 

28.0 

22.3 

25.0 

22.3 

26.5 

21.3 

33.5 

22.8 

26.5 

24.3 

27.0 

24.3 

24.0 

25.8 

23.5 

25.2 

25.0 

26.7 

29.5 

25.7 

23.5 

26.2 

22.5 

26.1 

25.5 

28.1 

24.0 

24.5 

26.0 

24.5 

29.0 

23.5 

26.0 

24.5 

29.6 

No.  of  measurements 
Corrected  growth. . . 

31.1 

11.0 

30.0 

13.5 

26.8 

12.5 

28.3 

11.5 

36.7 

13.0 

28.3 

14.5 

28.8 

11.0 

25.6 

11.5 

25.0 

16.0 

26.5 

13.5 

31.3 

11.5 

24.9 

11.0 

23.8 

14.0 

26.9 

13.5 

25.3 

14.0 

27.4 

11.5 

30.5 

12.5 

27.3 

9.5 

31.0 

12.5 

No.  of  measurements 
Corrected  growth . . . 

f  28  Total  growth . 

<  &  No.  of  meas’ments 
1 29.  Corrected  growth  . 

11.9 

4.0 

14.6 

3.0 

13.5 

3.0 

12.4 

4.0 

14.0 

3.5 

15.6 

4.0 

11.8 

4.5 

12.4 

4.5 

17.2 

4.5 

14.5 

4.5 

12.3 

5.0 

11.8 

5.0 

15.0 

6.0 

14.4 

7.0 

14.9 

7.5 

12.2 

7.5 

13.3 

8.0 

10.0 

7.0 

13.3 

5.5 

4.5 

10.0 

3.4 

10.5 

3.4 

16.5 

4.5 

10.0 

3.9 

11.0 

4.5 

10.5 

5.0 

11.5 

5.6 

7.5 

5.0 

7,5 

5.0 

8.0 

5.5 

10.0 

5.5 

9.5 

6.6 

9.5 

7.7 

11.0 

8.3 

9.0 

8.3 

9.0 

8.8 

10.5 

7.7 

9.6 

6.0 

10.0 

No.  of  measurements 
Corrected  growth. . . 

11.2 

7.0 

11.8 

6.5 

18.5 

8.5 

11.1 

9.5 

12.3 

8.0 

11.7 

9.6 

12.8 

11.0 

8.3 

9.5 

8.3 

10.0 

8.8 

10.5 

11.1 

10.0 

10.6 

10.0 

10.6 

12.0 

12.  i 

9.5 

9.9 

10.0 

9.9 

10.0 

11.5 

7.0 

10.5 

10.0 

11.0 

10.0 

No.  of  measurements 
Corrected  growth. . . 

8.0 

7.4 

9.7 

10.3 

9.1 

10.7 

12.4 

10.7 

11.3 

11.8 

11.2 

11.2 

13.5 

10.5 

11.2 

11.2 

7.8 

11.1 

11.1 

Table  F. — Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade — Continued.  317 


Group. 

691-700 

A.D. 

681-90 

671-80 

661-70 

V) 

lO 

641-50 

f 

621-30 

611-20 

601-10 

591-600 

581-90 

571-80 

561-70 

551-60 

541-50 

531-40  j 

521-30  j 

511-20 

501-10 

1414.5 
69 

380.0 

1581.5 
58 

485.0 

958.5 
49 

334.0 

888.0 

51 

348.0 

586.5 
47 

265.0 

386.0 

33 

195.0 

419.0 

47 

250.0 

263.5 
30 

179.0 

189.0 

25 

145.0 

306.0 

49 

321.0 

110.5 
17 
94.0 

166.0 

24 

153.0 

70.5 
11 
68.0 

9.5 

2 

9.4 

20.5 

4 

21.0 

28.5 

5 

29.9 

14.5 
2 

15.2 

5.5 
1 

6.0 

8.5 
1 

9.3 

10.5 
2 

11.7 

1129.0 

60 

296.5 

1575.0 

1054.0 

59 

274.0 

1527.0 

966.0 

53 

248.0 

1471.0 

878.0 

47 

(223.0 

1493.5 

764.5 

42 

192.0 

1447.0 

668.5 

32 

167.0 

1376.5 

577.0 

26 

139.3 

1386.0 

385.0 

14 

88.3 

1599.0 

102.0 

3 

23.4 

1739.5 

58 

464.0 

1000.0 

No.  of  measurements 
Corrected  growth. . . 

, 

1459.5 

52 

385.0 

1016.0 

iio3.b 

43 

298.0 

984.0 

1107.0 

.36 

289.0 

1032.5 

1012.5 

30 

261.0 

984.0 

801.0 

26 

204.0 

944.5 

712.0 

23 

174.0 

1060.0 

277.0 

12 

69.3 

1054.0 

216.0 

10 

52.7 

1032.5 

102.0 

5 

24.9 

1033.0 

72.0 

3 

16.8 

1031.0 

48 

291.0 

1156.5 

No.  of  measurements 
Corrected  growth . . . 
13.  Total  growth . 

475.0 

950.5 

456.0 

967.0 

435.0 

986.5 

47 

335.0 

938.0 

437.5 

988.5 
48 

331.0 

946.0 

418.0 

991.0 

391.0 

1024.0 

386.0 

951.0 

436.0 

1005.0 

No.  of  measurements 
Corrected  growth . . . 

328.0 

918.5 

331.0 

958.5 

3M.6 

957.5 

336.0 

998.0 

309.0 

1056.0 

324.0 

1132.5 

321.0 

1124.0 

321.0 

1135.0 

308.0 

1130.5 

320.0 

1160.5 

301.0 

1072.0 

286.0 

1041.5 

318.0 

1132.0 

312.0 

1150.0 

302.0 

1108.0 

298.0 

1170.0 

No.  of  measurements 
Corrected  growth . . . 

355.0 

607.0 

366.0 

590.5 

354.0 

644.5 

354.0 

605.0 

354.0 

584.5 

3W.0 

626.0 

382.0 

652.0 

406.0 

733.5 

.399.0 

696.0 

398.0 

710.0 

392.0 

778.0 

398.0 

799.5 

365.0 

745.0 

350.0 

774.5 

378.0 

813.0 

380.0 

738.0 

362.0 

779.0 

378.0 

821.0 

370.0 

817.5 

No.  of  measurements 
Corrected  growth. . . 

271.0 

389.5 

260.0 

401.0 

280.0 

406.5 

260.0 

432.5 

247.5 

421.5 

263.5 

428.0 

271.6 

426.5 

303.0 

440.0 

385.5 

459.0 

387.0 

483.0 

311.0 

472.0 

315.0 

458.0 

290.5 

477.6 

298.5 

491.0 

310.0 

496.0 

278.0 

471.0 

291.0 

490.0 

302.5 

491.5 

298.0 

485.0 

No.  of  measurements 
Corrected  growth. . . 
17.  Total  growth . 

195.0 

443.5 

198.5 

■450.5 

198.0 

443.5 

208.0 

433.0 

200.5 

463.0 

201.0 

474.0 

199.0 

410.5 

204.0 

501.0 

209.6 

499.5 

217.0 

511.0 

210.0 

651.5 

201.0 

630.0 

207.0 

543.5 

211.0 

531.5 

211.0 

557.0 

199.0 

564.0 

205.0 

594.0 

203.0 

637.0 

199.5 

635.0 

No.  of  measurements 
Corrected  growth. . . 
18.  Total  growth . 

261.0 

271.0 

261.0 

261.5 

2^.0 

260.5 

244.0 

261.0 

258.0 

266.0 

261.0 

268.0 

222.0 

269.0 

268.0 

266.0 

264.0 

268.0 

266.0 

282.0 

284.0 

321.0 

269.0 

313.0 

274.0 

344.0 

264.0 

298.5 

272.0 

294.0 

274.0 

308.5 

285.0 

336.0 

302.0 

336.0 

299.0 

325.0 

No.  of  measurements 
Corrected  growth. . . 

i^.o 

211.0 

174.0 

207.5 

171.0 

196.0 

169.0 

197.5 

170.0 

200.5 

169.0 

210.5 

167.0 

221.6 

164.0 

221.5 

163.0 

213.5 

169.0 

225.5 

189.0 

228.0 

182.0 

218.0 

197.0 

207.5 

169.0 

225.0 

165.0 

227.0 

170.0 

241.0 

183.0 

257.0 

181.0 

240.0 

172.0 

230.0 

No.  of  measurements 
Corrected  growth. . . 
20.  Total  growth . 

161.0 

413.0 

157.5 

416.0 

148.0 

402.5 

148.0 

391.0 

149.0 

374.5 

156.0 

416.0 

163.0 

428.6 

161.5 

443.5 

IM.O 

428.5 

161.0 

423.5 

161.0 

441.0 

153.0 

413.0 

144.0 

426.0 

154.0 

429.5 

154.0 

477.5 

162.0 

483.5 

170.0 

501.6 

157.0 

475.5 

148.0 

457.5 

No.  of  measurements 
Corrected  growth. . . 

334.0 

117.0 

334.0 

117.5 

322.0 

112.0 

311.0 

117.0 

296.0 

111.0 

328.0 

112.5 

336.0 

138.5 

346.0 

115.0 

323.0 

115.5 

326.0 

109.5 

339.0 

115.0 

316.0 

119.0 

324.0 

121.0 

326.0 

127.0 

358.0 

127.5 

358.0 

124.5 

368.0 

122.5 

346.0 

124.0 

330.0 

132.5 

No.  of  measurements 
Corrected  growth . . . 

99.0 

161.5 

99.0 

165.5 

M.6 

161.5 

97.5 

163.5 

92.5 

162.0 

93.5 

161.5 

114.5 

159.5 

95.0 

175.0 

95.0 

172.0 

89.6 

161.0 

93.5 

174.0 

96.5 

166.5 

97.5 

171.0 

102.0 

160.0 

102.0 

173.5 

99.0 

173.5 

97.0 

185.5 

98.0 

175.0 

104.0 

186.5 

No.  of  measurements 
Corrected  growth. . . 
M  Tnful  irrowth . 

148.0 

71.5 

151.0 

72.0 

147.6 

66.5 

148.5 

64.0 

146.5 

74.0 

146.5 

69.5 

id.6 

68.5 

156.0 

56.0 

IM.O 

74.0 

142.5 

79.5 

153.0 

73.5 

146.0 

77.0 

149.0 

68.5 

139.0 

72.5 

150.0 

75.5 

149.5 

72.6 

159.0 

72.0 

149.0 

65.5 

158.5 

69.5 

No.  of  measurements 
Corrected  growth. . . 
24.  Total  growth . 

68.8 

7.0 

69.0 

9.0 

63.5 

9.5 

61.0 

8.0 

70.2 

8.5 

65.7 

9.5 

64.5 

11.6 

52.5 

9.0 

69.2 

8.5 

74.0 

13.0 

68.3 

13.0 

71.3 

14.0 

63.0 

12.0 

66.7 

13.0 

69.0 

14.6 

66.0 

13.0 

65.2 

8.5 

59.0 

10.5 

62.5 

12.0 

No.  of  measurements 
Corrected  growth. . . 
25.  Total  growth... . 

6.9 

23.0 

8.9 

26.5 

9.4 

27.0 

7.9 

26.5 

8.3 

23.5 

9.3 

28.5 

11.3 

26.5 

8.8 

26.6 

7.8 

28.6 

12.6 

30.5 

12.6 

35.0 

13.5 

33.5 

11.5 

25.0 

12.5 

26.0 

13.8 

26.0 

12.4 

24.0 

8.0 

25.5 

9.9 

26.0 

11.3 

28.0 

No.  of  measurements 
Corrected  growth. . . 

23.4 

26.5 

26.8 

30.5 

27.3 

31.0 

26.8 

33.5 

23.7 

31.0 

28.7 

33.0 

26.7 

29.6 

26.7 

33.0 

28.7 

32.5 

30.6 

25.0 

35.1 

33.5 

33.5 

38.0 

24.9 

38.0 

25.8 

28.5 

25.8 

26.0 

23.8 

32.0 

25.2 

30.0 

25.6 

30.5 

27.5 

26.0 

No.  of  measurements 
Corrected  growth . . . 
27.  Total  growth. . . 

27.8 

10.5 

31.9 

10.5 

32.4 

11.0 

35.0 

11.0 

32.4 

15.0 

34.4 

13.0 

30.7 

14.0 

34.3 

10.6 

33.8 

10.5 

25.9 

11.5 

34.7 

14.5 

39.3 

14.0 

39.3 

10.0 

29.4 

12.0 

26.8 

11.0 

32.9 

10.6 

30.8 

12.0 

31.3 

12.5 

26.7 

11.0 

No.  of  measurements 
Corrected  growth. . . 

(  28  Total  growth . 

'<  A  No.  of  meas’ments 
(  29.  Corrected  growth . 

30.  Total  growth . 

No.  of  measurements 
Corrected  growth. . . 

31.  Total  growth . 

11.1 

5.0 

11.1 

5.5 

11.6 

5.0 

11.6 

6.0 

15.8 

6.5 

13.7 

6.0 

14.7 

7.0 

11.0 

7.0 

11.0 

5.5 

12.1 

6.0 

15.2 

6.0 

14.6 

5.5 

10.5 

5.0 

12.6 

6.0 

11.6 

5.0 

ib.4 

5.0 

12.5 

4.5 

13.0 

5.5 

11.5 

5.5 

5.5 

9.0 

6.0 

9.5 

5.5 

7.5 

6.5 

9.0 

7.1 

7.0 

6.5 

9.0 

7.6 

9.0 

7.6 

8.5 

5.9 

8.5 

6.5 

8.0 

6.5 

10.0 

5.9 

10.5 

5.4 

8.5 

6.5 

7.6 

5.4 

9.0 

5.4 

13.0 

4.8 

11.5 

5.9 

10.0 

5.9 

12.5 

9.8 

10.0 

10.3 

10.5 

8.2 

10.0 

9.8 

10.0 

7.5 

10.0 

9.8 

11.0 

9.8 

10.0 

9.2 

11.6 

9.2 

8.5 

8.6 

8.6 

10.8 

9.5 

11.3 

7.5 

9.1 

10.5 

8.1 

10.0 

7.6 

9.0 

13.9 

7.0 

12.3 

8.0 

10.7 

8.5 

13.3 

7.5 

No.  of  measurements 
Corrected  growth . . . 

11.1 

11.7 

11.1 

ii.i 

11.0 

12.6 

11.0 

12.7 

9.3 

9.3 

10.5 

8.2 

11.5 

10.9 

9.8 

7.6 

8.7 

9.2 

8.1 

318  Table  F. — Growth  of  Sequoia  waskingtonianahy  Groups  for  each  Decade — Continued. 


Group. 

491-500 

A.D. 

o 

? 

00 

471-80 

461-70 

451-60 

441-50 

431-40 

421-30 

o 

M 

1 

o 

1 

391-400 

381-90 

371-80 

361-70 

351-60 

341-50 

331-40 

321-30 

311-20 

301-10 

1005.0 

46 

278.0 

1122.0 

51 

356.0 

845.5 

47 

306.0 

506.0 

33 

204.5 

630.6 
47 

293.0 

333.5 
30 

176.0 

240.5 
25 

153.0 

478.5 
49 

342.0 

125.0 

17 

97.0 

185.0 

24 

156.0 

72.0 

11 

64.3 

13.5 
2 

12.6 
20.0 

4 

19.6 

27.6 

5 

28.1 

14.5 
2 

15.0 

5.5 
1 

5.9 

12.5 
1 

13.3 
7.0 
2 

7.6 

1006.5 

44 

273.0 

1136.0 

970.0 

44 

256.0 

1149.0 

943.5 
42 

249.0 

996.5 
51 

307.0 

883.5 

898.0 

37 

234.0 

962.0 

50 

293.0 

867.0 

801.0 

31 

199.0 

886.5 

408.0 

17 

101.5 

933.0 

336.0 

12 

79.6 

looao 

No.  of  measurements 
Corrected  growth . . . 

912.0 

965.5 

50 

267.0 

878.0 

923.0 

48 

253.0 

890.5 

767.0 

44 

208.0 

988.0 

749.0 

36 

200.0 

951.5 

596.5 
26 

157.5 
966.0 

490.5 
21 

129.5 
960.0 

463.0 

17 

122.5 

931.0 

282.5 
11 

74.7 

924.0 

47 

282.0 

674.5 

357.5 
11 

91.0 

896.5 
45 

268.0 

641.5 

229.0 

9 

55.0 

809.0 

44 

242.5 

631.5 

No.  of  measurements 
Corrected  growth _ 

356.0 

860.0 

357.0 

839.5 

266.0 

923.5 

274.0 

894.5 

289.0 

897.0 

250.0 

871.0 

857.0 

42 

252.5 

665.5 
33 

220.5 
1032.5 

No.  of  measurements 
Corrected  growth . . . 

307.0 

532.0 

297.0 

558.5 

308.0 

514.0 

300.0 

566.0 

317.0 

569.5 

302.5 

568.5 

302.0 

693.0 

290.5 

560.0 

200.0 

558.5 

390.5 

561.0 

319.0 

561.5 

304.5 

604.5 

306.0 

625.0 

301.5 

696.0 

289.0 

655.5 

No.  of  measurements 
Corrected  growth . . . 

212.0 

637.0 

220.0 

662.0 

200.0 

673.0 

218.0 

649.0 

217.5 

680.5 

214.5 

733.0 

221.5 

777.0 

207.5 

748.0 

213.5 

763.6 

203.0 

717.0 

201.0 

753.0 

214.0 

786.5 

219.0 

838.0 

207.0 

863.0 

226.0 

814.0 

230.0 

905.5 

216.0 

979.6 

211.0 

971.5 

No.  of  measurements 
Corrected  growth . . . 

18.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . 

292.0 

336.0 

300.0 

381.5 

300.0 

355.5 

286.0 

358.0 

299.0 

394.0 

317.0 

391.0 

334.0 

387.5 

318.0 

412.5 

321.0 

428.5 

298.0 

433.6 

319.0 

460.6 

351.0 

442.5 

336.0 

424.5 

342.0 

450.5 

319.0 

423.5 

352.0 

452.6 

37A0 

427.0 

370.0 

425.5 

389.0 

472.5 

174.0 

249.0 

195.0 

234.5 

1790 

244.0 

179.0 

231.5 

194.6 

230.5 

192.0 

239.0 

187.0 

259.5 

198.0 

279.5 

203.0 

269.5 

202.0 

277.0 

211.5 

283.0 

201.0 

296.6 

191.0 

243.5 

201.0 

291.5 

186.5 

294.5 

197.6 

285.5 

185.0 

281.5 

18^0 

281.5 

200.0 

288.5 

No.  of  measurements 
Corrected  growth . . . 

156.5 

458.0 

145.5 

479.0 

149.0 

498.5 

139.0 

511.0 

137.0 

485.0 

140.0 

495.0 

150.0 

500.5 

159.5 

507.5 

151.5 

516.6 

154.0 

554.0 

155.5 

581.5 

161.0 

604.5 

130.0 

628.0 

154.0 

613.6 

154.0 

619.0 

147.0 

645.5 

143.5 

634.5 

142.0 

655.6 

144.5 

634.0 

No.  of  measurements 
Corrected  growth . . . 

324.0 

136.0 

336.0 

133.0 

345.0 

129.5 

349.0 

133.5 

327.0 

143.0 

328.0 

140.0 

328.0 

158.0 

329.0 

142.5 

330.0 

161.6 

349.0 

155.5 

361.0 

166.0 

370.0 

167.5 

380.0 

178.5 

366.0 

171.5 

365.0 

173.0 

375.0 

174.6 

363.0 

178.0 

371.0 

177.0 

355.0 

186.0 

No.  of  measurements 
Corrected  growth. . . 

105.0 

183.5 

102.0 

190.5 

98.0 

186.5 

100.0 

181.0 

106.0 

186.0 

103.0 

199.0 

115.0 

195.5 

102.5 

196.5 

115.0 

201.0 

110.0 

213.0 

115.5 

207.5 

115.0 

207.5 

121.0 

219.0 

114.5 

211.0 

114.5 

213.0 

114.0 

215.0 

114.5 

206.0 

112.0 

203.5 

116.0 

215.5 

No.  of  measurements 
Corrected  growth . . . 

154.0 

74.0 

159.6 

74.5 

155.6 

79.0 

150.0 

85.0 

153.5 

79.0 

163.5 

80.0 

160.0 

79.5 

160.0 

83.0 

162.5 

78.0 

171.0 

83.5 

166.0 

79.0 

16A0 

81.0 

173.5 

81.5 

166.0 

91.0 

166.0 

84.5 

leko 

83.0 

157.5 

77.0 

154.0 

78.0 

162.0 

87.6 

No.  of  measurements 
Corrected  growth . . . 

66.0 

14.0 

66.0 

15.0 

69.6 

16.0 

74.6 

16.0 

69.0 

14.0 

69.6 

12.5 

69.0 

13.0 

71.5 

13.5 

67.0 

12.0 

71.3 

14.5 

67.2 

16.0 

68.5 

16.5 

68.6 

13.0 

76.2 

11.0 

70.5 

12.0 

68.7 

11.6 

M.5 

12.0 

64.0 

11.0 

71.5 

11.6 

No.  of  measurements 
Corrected  growth . . . 

13.0 

20.5 

13.9 

24.0 

14.8 

29.5 

14.7 

24.5 

12.8 

25.5 

11.4 

25.5 

11.8 

23.0 

12.3 

24.5 

10.8 

34.0 

13.0 

36.0 

14.3 

30.0 

13.8 

26.5 

11.5 

26.5 

9.6 

25.5 

10.5 

20.0 

10.1 

28.0 

10.6 

24.5 

9.6 

23.5 

9.9 

23.0 

No.  of  measurements 
Corrected  growth _ 

20.0 

32.0 

23.4 

34.5 

28.7 

34.5 

23.7 

31.5 

24.6 

31.0 

24.5 

35.5 

22.0 

35.5 

23.4 

36.5 

32.4 

34.0 

34.2 

26.6 

28.4 

29.5 

25.0 

32.0 

24.9 

28.5 

23.8 

32.5 

18.6 

28.5 

26.8 

28.5 

22.6 

28.5 

21.6 

34.5 

20.9 

33.0 

No.  of  measurements 
Corrected  growth. . . 

32.7 

14.0 

35.2 

12.0 

35.1 

13.5 

32.0 

16.0 

31.5 

16.0 

36.0 

15.0 

36.0 

16.0 

3^9 

12.0 

34.3 

16.0 

26.8 

15.5 

29.5 

16.6 

32.0 

18.5 

28.4 

18.0 

32.3 

19.5 

28.3 

16.0 

28.2 

13.6 

28.2 

13.0 

33.9 

15.5 

32.4 

19.0 

No.  of  measurements 
Corrected  growth .. . 

f  28  Total  growth . 

i  &  No.  of  meas’ments 
1 29.  Corrected  growth . 

14.5 

5.5 

12.4 

6.0 

14.0 

6.5 

16.5 

6.0 

16.5 

5.0 

15.4 

4.5 

16.4 

6.0 

12.3 

3.5 

16.3 

4.0 

15.8 

5.6 

16.8 

5.0 

18.9 

5.0 

18.3 

4.5 

19.8 

4.0 

16.2 

3.5 

13.7 

3.6 

13.2 

4.0 

15.7 

4.0 

19.1 

4.5 

6.9 

11.0 

5.3 

12.0 

5.9 

11.0 

6.3 

8.5 

5.3 

9.0 

4.8 

8.5 

6.3 

8.5 

3.7 

8.5 

4.2 

7.5 

5.8 

6.0 

5.3 

6.0 

5.3 

6.0 

4.7 

6.5 

4.2 

7.6 

3.7 

11.0 

3.7 

8.0 

4.2 

7.0 

4.2 

7.0 

4.7 

5.0 

No.  of  measurements 
Corrected  growth _ 

11.7 

7.0 

12.8 

7.0 

11.7 

7.0 

9.0 

9.0 

9.6 

9.0 

9.0 

10.0 

9.0 

8.0 

9.0 

8.0 

7.9 

9.0 

ks 

9.0 

6.3 

9.5 

6.3 

10.5 

k8 

10.0 

7.9 

9.0 

11.5 

10.5 

8.4 

11.0 

7.3 

17.0 

7.3 

12.5 

5.2 

11.5 

No.  of  measurements 
Corrected  growth . . . 

7.6 

7.6 

7.6 

9.7 

9.7 

10.8 

8.6 

8.6 

9.6 

9.6 

10.2 

11.2 

10.7 

9.6 

11.2 

h.7 

18.0 

13.2 

12.2 

Table  F. — Growth  of  Sequoia  washingtoniana  hy  Groups  for  each  Decade — Continued 


319 


Group. 

291-.^00 

A.  D. 

00 

M 

271-80 

261-70 

o 

1 

in 

M 

241-50 

231-40 

o 

7 

211-20 

o 

1 

o 

M 

191-200 

181-90 

171-80 

161-70 

151-60 

141-50 

f 

121-30 

111-20  1 

1  OI-IOI 

IS.  Total  growth . 

947.5 
42 

273.0 

626.5 
33 

205.0 

1055.5 

47 

392.0 

461.0 

30 

193.0 

292.5 
25 

145.0 

624.5 
49 

344.0 

167.0 

17 

103.0 

216.0 

24 

160.0 

87.0 

11 

70.8 
10.0 

2 

8.6 

21.5 

4 

19.5 

32.5 

5 

31.8 
16.0 

2 

16.0 

4.0 

1 

4.2 
7.0 
1 

7.3 
8.5 
2 

9.0 

838.5 
40 

249.5 

601.5 

806.0 

34 

228.0 

678.6 

783.5 
32 

219.0 

609.5 

661.0 

31 

180.0 

569.5 

33 

177.2 

1180.0 

667.5 
28 

179.6 

546.6 
32 

167.6 
1195.5 

474.0 

21 

125.0 

637.5 
31 

163.5 
1250.5 

387.6 

14 

100.5 

677.0 

31 

172.0 

1256.0 

369.5 

11 

91.2 

655.0 

29 

164.0 

1250.6 

162.0 

4 

40.0 

602.5 

29 

174.0 

1237.0 

No.  of  measurements 
Corieoted  growth. . . 

- 

675.6 

27 

190.5 

1155.5 

396.0 

19 

11.3.5 

1054.0 

357.5 

17 

101.0 

1012.5 

303.0 

15 

84.5 

1019.0 

181.0 

12 

49.8 

1029.0 

189.0 

10 

49.8 

1059.0 

103.0 

5 

28.3 

963.6 

47 

300.0 

655.0 

110.0 

4 

29.0 

986.5 

45 

305.0 

616.0 

134.0 

4 

33.8 

889.0 

43 

270.0 

608.0 

No.  of  measurements 
Corrected  growth. . . 

195.0 

1115.5 

217.0 

1095.0 

193.0 

1215.5 

885.5 
42 

266.0 

670.5 

No.  of  measurements 
Corrected  growth . . . 

410.0 

452.0 

398.0 

453.0 

437.0 

476.0 

420.0 

504.5 

422.0 

512.5 

437.0 

514.0 

435.0 

514.0 

429.0 

533.5 

420.0 

552.0 

388.0 

549.0 

351.0 

616.0 

334.0 

604.6 

332.6 

636.0 

332.0 

640.0 

333.0 

632.5 

No.  of  measurements 
Corrected  growth . . . 

187.0 

303.5 

185.6 

324.0 

192.0 

325.5 

201.0 

358.5 

203.0 

348.0 

201.0 

364.5 

198.0 

377.5 

204.0 

359.0 

209.0 

373.0 

206.0 

404.5 

228.0 

363.6 

222.0 

379.0 

231.0 

396.5 

230.0 

445.0 

226.0 

481.6 

231.0 

433.0 

215.0 

445.5 

210.5 

444.0 

195.0 

469.0 

No.  of  measurements 
Corrected  growth. . . 

149.6 

602.5 

156.0 

617.5 

155.0 

620.5 

169.0 

654.5 

162.0 

679.0 

167.5 

682.0 

172.0 

726.0 

161.5 

673.5 

166.5 

688.0 

197.0 

683.5 

168.5 

706.6 

164.0 

685.0 

169.0 

728.0 

188.0 

715.0 

201.0 

735.0 

17^0 

776.5 

186.0 

782.0 

179.5 

802.0 

187.5 

821.5 

'  No’,  of  measurements 
Corrected  growth. . . 

328.0 

186.5 

333.0 

190.5 

330.0 

212.6 

344.0 

205.5 

352.0 

200.0 

352.0 

210.5 

371.0 

200.0 

339.0 

202.0 

343.0 

204.0 

336.0 

200.0 

343.0 

206.5 

328.0 

199.5 

343.0 

195.0 

333.0 

219.5 

340.0 

215.5 

357.0 

230.0 

356.0 

242.0 

362.0 

231.5 

368.0 

217.5 

No.  of  measurements 
Corrected  growth. . . 

113.5 

235.5 

114.5 

231.0 

126.0 

229.5 

120.0 

231.5 

115.0 

237.0 

120.5 

232.0 

112.0 

236.0 

112.0 

245.0 

112.0 

231.0 

108.0 

238.6 

110.0 

214.5 

106.0 

230.0 

102.0 

227.0 

214.0 

238.0 

100.5 

232.5 

117.0 

245.0 

121.0 

242.0 

114.6 

248.0 

106.0 

247.0 

No.  of  measurements 
Corrected  growth . . . 

173.0 

83.0 

168.6 

79.5 

165.0 

81.0 

165.0 

85.5 

166.0 

92.5 

160.5 

91.0 

161.0 

92.5 

165.0 

91.0 

164.0 

84.5 

156.5 

81.0 

139.0 

88.5 

146.0 

91.0 

142.5 

95.0 

147.5 

96.0 

142.0 

86.5 

148.0 

91.5 

144.0 

82.0 

146.0 

95.0 

14^5 

109.0 

No.  of  measurements 
Corrected  growth . . . 

67.0 

13.0 

64.0 

13.0 

64.5 

11.5 

67.5 

13.0 

72.5 

16.0 

70.5 

16.0 

71.0 

17.5 

69.0 

16.6 

63.5 

15.5 

60.3 

12.0 

65.2 

15.0 

66.2 

14.0 

68.3 

15.5 

68.0 

15.6 

60.5 

21.0 

6.i3 

20.5 

56.0 

14.5 

64.0 

18.5 

72.5 

16.5 

No.  of  measurements 
Corrected  growth. . . 

11.1 

27.5 

11.1 

24.0 

9.7 

26.0 

11.0 

26.0 

13.4 

28.6 

13.4 

32.5 

14.6 

35.0 

13.7 

33.5 

12.8 

30.6 

9.8 

32.0 

12.2 

31.5 

11.3 

29.0 

12.5 

34.5 

12.4 

31.5 

16.6 

33.0 

16.1 

32.0 

ii.3 

38.5 

14.2 

33.5 

12.6 

31.6 

No.  of  measurements 
Corrected  growth . . . 

24.8 

32.5 

21.6 

36.5 

23.2 

38.5 

23.2 

39.0 

25.2 

37.5 

28.6 

35.0 

30.7 

35.5 

29.3 

42.6 

26.5 

43.0 

27.8 

40.5 

27.2 

38.0 

24.9 

35.5 

29.6 

30.5 

26.8 

28.0 

27.9 

29.0 

27.0 

25.6 

32.3 

27.6 

27.9 

27.5 

26.1 

32.0 

No.  of  measurements 
Corrected  gro-wth. . . 

31.7 

15.5 

35.5 

20.0 

37.3 

18.5 

38.6 

16.0 

36.1 

16.0 

33.6 

16.0 

33.9 

19.5 

40.4 

17.0 

40.8 

16.5 

38.2 

14.0 

35.7 

16.0 

33.1 

15.5 

28.4 

16.5 

25.9 

17.5 

26.7 

11.5 

23.3 

12.0 

25.1 

14.0 

24.9 

8.5 

28.9 

11.5 

No.  of  measurements 
Corrected  growth. . . 

(  28  Total  growth . 

-1  &  No.  of  meas’ments 
(  29.  Corrected  growth. 

15.5 

4.0 

20.0 

4.0 

18.5 

7.0 

15.9 

9.0 

15.9 

8.5 

15.8 

8.5 

19.3 

90 

16.7 

9.5 

16.2 

8.0 

13.6 

7.5 

15.5 

8.5 

15.0 

8.5 

15.0 

8.5 

16.8 

8.5 

11.0 

6.0 

11.5 

7.0 

13.3 

8.0 

8.0 

7.5 

10.8 

7.5 

4.2 

7.0 

4.2 

7.0 

7.3 

8.0 

9.3 

6.0 

8.8 

4.0 

8.8 

5.5 

9.3 

7.0 

9.8 

8.0 

8.3 

8.0 

7.7 

9.0 

8.8 

6.0 

8.7 

7.0 

8.7 

9.0 

8.7 

6.5 

6.1 

6.5 

7.2 

6.5 

8.2 

7.5 

7.7 

8.0 

7.6 

9.0 

No.  of  measurements 
Corrected  growth. . . 

7.3 

9.0 

7.3 

11.5 

8.3 

12.0 

6.2 

11.5 

4.1 

12.5 

5.7 

9.6 

7.3 

7.5 

8.3 

10.0 

8.3 

10.0 

9.3 

10.0 

6.2 

11.5 

7.2 

11.5 

9.2 

10.0 

6.6 

11.0 

6.6 

12.0 

5.6 

8.5 

7.7 

8.5 

8.1 

8.0 

9.1 

11.5 

No.  of  measurements 
Corrected  growth 

8.5 

12.1 

12.6 

12.1 

13.1 

10.6 

7.9 

10.5 

10.5 

10.4 

12.6 

12.0 

10.4 

11.4 

12.5 

8.8 

1  8.8 

8.3 

11.9 

320 


Table  F. — Growth  of  Sequoia  washingioniana  by  Groups  for  eM.ch  Decade — Continued 


Group. 

a  V 

001-16 

17.  Total  growth . 

692.5 

No.  of  measurements 

36 

Corrected  growth . . . 

203.0 

18.  Total  growth . 

673.5 

No.  of  measurements 

30 

Corrected  growth . . . 

194.5 

19.  Total  growth . 

458.0 

No.  of  measurements 

25 

Corrected  growth . . . 

181.0 

20.  Total  growth . 

843.0 

No.  of  measurements 

49 

Corrected  growth . . . 

371.0 

21.  Total  growth . 

237.5 

No.  of  measurements 

17 

Corrected  growth _ 

114.5 

22.  Total  growth . 

255.6 

No.  of  measurements 

24 

Corrected  growth. . . 

146.0 

23.  Total  growth . 

100.5 

No.  of  measurements 

11 

Corrected  growth. . . 

65.7 

24.  Total  growth . 

16.0 

No.  of  measurements 

2 

Corrected  growth . . . 

12.1 

25.  Total  growth . 

31.0 

No.  of  measurements 

4 

Corrected  growth . . . 

25.6 

26.  Total  growth . 

33.5 

No.  of  measurements 

5 

Corrected  growth _ 

30.2 

27.  Total  growth . 

13.5 

No.  of  measurements 

2 

Corrected  growth. . . 

12.7 

r  28  Total  growth . 

6.5 

t  &,  J4o.  of  meas'ments 

1 

1  29.  Corrected  growth . 

6.6 

30.  Total  growth . 

8.5 

No.  of  measurements 

1 

Corrected  growth. . . 

8.6 

31.  Total  growth . 

12.5 

No.  of  measurements 

2 

Correeted  growth . . . 

12.9 

Group. 


19.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

20.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

21.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

22.  Total  grotrth . 

No.  of  measurements. _ 

Corrected  growth . 

23.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

24.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

25.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

26.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

27.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

28  Total  growth . 

&  No.  of  measurements . 

29.  Corrected  growth . 

30.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 

31.  Total  growth . 

No.  of  measurements . 

Corrected  growth . 


81-90 

71-80 

61-70 

51-60 

1 

o 

in 

1 

9^ 

31-40 

21-30 

o 

7 

Qo 

■<  « 

10-1 

B.  C. 

20-11 

30-21 

40-31 

50-41 

1  60-51 

70-61 

80-71 

90-81 

Ifr-OOI 

741  n 

733  a 

485.0 

505.0 

263.5 

247.0 

122.0 

34 

34 

30 

25 

23 

11 

7 

4 

213  0 

206  0 

136.0 

136.0 

68.2 

65.0 

31.1 

596.5 

613.5 

580.5 

693.5 

608.0 

597.5 

550.6 

579.0 

574.5 

568.5 

604.5 

264.0 

219.5 

134.5 

135.0 

146.5 

106.5 

69.0 

30 

24 

14 

11 

7 

7 

7 

5 

2 

200.5 

203.0 

190.0 

191.5 

193.5 

186.0 

168.5 

173.0 

167.6 

162.0 

144.0 

77.0 

64.0 

39.3 

38.5 

40.1 

27.8 

18 

460.0 

450.0 

471.0 

526.6 

482.5 

479.0 

506.5 

529.0 

544.0 

528.0 

514.5 

478.5 

461.0 

486.0 

484.6 

476.5 

466.0 

457.6 

420.0 

25 

180.0 

-173.5 

180.0 

199.0 

180.0 

177.5 

186.0 

193.0 

196.0 

188.5 

181.5 

167.0 

159.2 

167.0 

164.0 

160.0 

154.0 

148.5 

134.0 

873.5 

1008.5 

959.5 

1018.5 

1018.5 

1100.0 

1002.5 

1066.5 

1060.5 

1031.0 

1050.5 

1061.0 

1036.5 

1021.5 

943.0 

937.0 

994.5 

923.6 

966.5 

378.0 

431.0 

406.0 

428.0 

423.0 

452.0 

407.0 

428.0 

422.0 

405.0 

410.0 

408.6 

395.0 

387.0 

352.0 

347.0 

365.0 

335.0 

348.0 

243.0 

276.5 

293.0 

278.0 

289.5 

257.0 

271.5 

263.0 

263.0 

274.0 

303.0 

331.0 

320.6 

354.5 

346.0 

332.0 

322.5 

324.6 

322.0 

115.5 

130.5 

137.0 

129.0 

128.5 

117.0 

122.0 

116.0 

115.0 

118.5 

13C.0 

140.5 

135.0 

147.0 

142.5 

134.5 

129.0 

129.0 

126.0 

277.0 

276.0 

280.0 

297.0 

326.0 

291.5 

297.0 

317.0 

288.5 

291.0 

295.5 

291.0 

302.0 

308.5 

306.5 

320.0 

345.5 

376.5 

368.0 

157.0 

154.0 

155.0 

162.0 

176.0 

156.0 

157.5 

166.0 

149.5 

149.0 

149.0 

145.0 

148.0 

149.6 

147’.5 

152.0 

164.0 

176.6 

170.5 

108.5 

123.5 

125.0 

113.5 

123.5 

114.0 

120.5 

121.5 

118.0 

118.0 

117.0 

125.0 

117.0 

111.6 

118.0 

121.0 

120.0 

134.5 

153.0 

70.0 

78.8 

78.5 

70.6 

75.7 

68.9 

71.7 

71.5 

68.5 

67.6 

66.2 

70.0 

64.7 

61.0 

63.8 

64.7 

63.5 

70.5 

79.3 

17.5 

16.5 

14.5 

13.5 

15.5 

13.5 

17.0 

14.5 

18.5 

17.5 

26.6 

17.0 

22.5 

25.5 

22.5 

22.5 

24.0 

22.5 

21.6 

13.1 

12.2 

10.6 

9.6 

11.0 

9.5 

11.8 

9.9 

12.4 

11.6 

16.6 

10.9 

14.3 

16.0 

13.9 

13.8 

14.5 

13.4 

12.6 

34.0 

32.0 

32.5 

36.0 

39.0 

35.5 

36.5 

35.5 

33.0 

30.5 

33.0 

38.0 

36.0 

34.6 

33.0 

35.5 

27.0 

25.5 

26.6 

27.9 

26.0 

26.2 

28.8 

30.8 

27.7 

28.2 

27.2 

25.0 

22.9 

24.4 

27.8 

25.9 

24.5 

23.2 

24.6 

18.6 

17.2 

17.6 

27.5 

34.0 

29.0 

33.5 

32.0 

33.5 

31.0 

34.5 

33.0 

39.6 

30.0 

30.0 

29.0 

33.0 

30.5 

34.0 

31.0 

39.5 

41.5 

24.7 

30.3 

25.8 

29.7 

28.2 

29.4 

27.0 

30.0 

28.6 

25.4 

25.7 

25.6 

24.6 

27.8 

25.6 

28.4 

26.7 

32.5 

33.7 

11.5 

14.0 

14.5 

13.5 

15.5 

14.5 

14.5 

11.5 

12.0 

14.5 

16.0 

15.5 

17.0 

15.0 

14.5 

16.0 

13.5 

16.0 

17.5 

10.7 

13.0 

13.4 

12.4 

14.2 

13.2 

13.1 

10.4 

10.8 

13.0 

14.3 

13.8 

15.0 

13.2 

12.7 

13.1 

11.7 

13.8 

15.1 

5.5 

6.0 

5.5 

0.5 

4.5 

4.5 

5.0 

5.0 

6.0 

6.5 

6.0 

8.5 

8.0 

8.6 

7.5 

7.0 

7.5 

6.0 

5.5 

5.6 

6.1 

5.5 

5.5 

4.5 

4.5 

5.0 

5.0 

6.0 

6.5 

5.9 

8.4 

7.8 

8.3 

7.3 

6.8 

L3 

5.8 

A3 

7.5 

9.0 

8.5 

8.0 

10.0 

11.0 

12.0 

10.0 

7.5 

7.5 

10.0 

10.5 

10.0 

9.0 

9.0 

9.0 

8.0 

7.6 

6.5 

7.6 

9.0 

8.5 

8.0 

10.0 

11.0 

12.0 

10.0 

7.5 

7.4 

9.9 

10.3 

9.8 

8.8 

8.8 

8.7 

7.7 

7.2 

6.2 

9.5 

10.5 

11.5 

10.5 

10.5 

9.0 

9.5 

8.0 

10.0 

10.5 

13.0 

12.5 

12.5 

10.5 

14.0 

10.5 

13.5 

15.5 

12.0 

9.8 

10.8 

11.9 

10.8 

10.8 

9.2 

9.7 

8.2 

10.2 

10.7 

13.2 

12.7 

12.7 

10.6 

14.0 

10.6 

13.5 

15.5 

12.0 

I  9 

A 

1 

1 

in 

A 

s 

A 

00 

A 

J, 

V 

S 

1 

t 

M 

o 

1 

2  w 

ro 

in 

z 

S5 

S 

M 

m 

m 

z 

00 

N 

g 

N 

C>4 

M 

M 

C>4 

fO 

43.'j.0 

392.0 

290.5 

289.0 

260.5 

247.5 

207.5 

203.5 

137.5 

23 

22 

21 

19 

17 

15 

13 

12 

7 

138.0 

90.3 

89.0 

87.5 

77.8 

72.3 

59.5 

65.2 

38.7 

953.5 

890.5 

875.0 

764.0 

775.0 

705.6 

632.0 

650.5 

640.5 

660.5 

667.5 

450.6 

469.0 

445.5 

485.0 

374.6 

314.5 

179.6 

128.0 

49 

49 

43 

36 

84 

30 

22 

18 

7 

4 

314.0 

305.0 

263.0 

265.0 

238.0 

209.0 

211.0 

204.0 

205.0 

205.0 

137.0 

142.6 

133.5 

141.0 

109.0 

87.0 

49.5 

34.8 

168.5 

326.0 

314.0 

338.5 

357.5 

346.6 

353.5 

449.0 

410.0 

373.5 

301.0 

408.0 

341.0 

320.5 

354.5 

325.0 

292.0 

253.6 

192.5 

169J) 

17 

17 

15 

15 

14 

12 

12 

12 

12S.0 

124.0 

130.5 

136.5 

131.0 

132.0 

166.0 

150.0 

135.5 

108.0 

145.0 

120.0 

113.0 

119.0 

109.0 

96.6 

83.0 

65.0 

66.7 

55.0 

362.6 

24 

351.5 

381.0 

394.0 

394.5 

394.5 

409.0 

429.0 

424.0 

464.0 

464.0 

481.6 

491.0 

640.5 

598.5 

634.5 

584.6 

570.6 

547.6 

637.6 

166.0 

158.5 

171.0 

174.0 

172.0 

170.0 

175.0 

181.0 

176.5 

192.0 

189.5 

195.0 

196.5 

214.0 

235.0 

246.0 

225.0 

217.0 

206.0 

203.0 

141.5 

11 

161.0 

159.5 

151.5 

148.5 

150.0 

167.5 

164.5 

178.0 

170.0 

156.0 

185.0 

187.0 

176.0 

174.6 

207.0 

243.0 

215.0 

249.0 

240.6 

72.2 

81.3 

79.6 

74.4 

72.6 

72.6 

80.5 

78.2 

83.5 

78.8 

71.6 

83.5 

83.6 

77.5 

76.2 

89.5 

104.0 

91.0 

104.5 

100.0 

18.5 

2 

19.5 

23.5 

17.5 

15.5 

21.5 

22.0 

23.0 

24.5 

24.0 

24.0 

24.5 

34.0 

33.0 

33.6 

33.0 

32.5 

36.5 

36.0 

27.6 

10.7 

11.2 

13.4 

9.8 

8.6 

11.8 

11.9 

12.3 

13.0 

12.6 

12.4 

12.5 

17.2 

16.5 

16.5 

16.2 

15.8 

17.1 

ILl 

12.9 

25.6 

4 

28.0 

27.0 

30.5 

33.5 

38.0 

39.5 

44.5 

37.0 

43.5 

43.5 

44.0 

41.0 

49.0 

51.6 

51.0 

53.0 

56.0 

64.0 

69.0 

16.7 

18.1 

17.3 

19.4 

20.8 

23.3 

23.9 

26.6 

21.9 

25.4 

25.0 

25.0 

23.0 

27.2 

28.4 

27.8 

28.6 

30.0 

33.6 

3A8 

30.0 

5 

32.5 

32.5 

36.5 

40.0 

41.5 

38.0 

39.5 

41.0 

43.5 

47.5 

48.5 

49.0 

38.5 

52.0 

48.0 

47.0 

60.0 

62.0 

47.5 

24.2 

26.0 

25.7 

28.5 

31.0 

31.8 

28.5 

29.3 

30.0 

31.4 

33.7 

34.0 

33.9 

26.3 

35.0 

31.9 

30.8 

32.3 

33.1 

29.8 

18.0 

2 

18.5 

15.5 

14.0 

13.5 

15.0 

16.5 

16.0 

14.0 

14.0 

12.0 

14.5 

17.0 

17.5 

22.0 

16.6 

18.6 

24.0 

20.5 

17.5 

15.4 

15.8 

13.1 

11.8 

11.3 

12.5 

13.7 

13.3 

ii.5 

11.4 

9.7 

11.6 

13.4 

13.7 

17.1 

12.6 

14.0 

18.0 

15.2 

12.8 

6.0 

1 

5.0 

6.0 

5.0 

5.0 

8.5 

6.5 

6.5 

6.0 

6.5 

6.0 

5.0 

4.0 

6.0 

5.5 

6.5 

9.0 

10.5 

11.5 

13.0 

5.8 

4.8 

4.8 

4.7 

4.7 

8.0 

5.1 

6.1 

5.5 

6.0 

5.5 

4.6 

3.6 

5.4 

4.5 

5.8 

8.0 

9.3 

10.2 

11.5 

6.5 

1 

7.0 

7.5 

5.5 

7.0 

8.0 

6.6 

8.0 

10.0 

8.6 

10.0 

8.0 

8.5 

9.0 

9.0 

8.5 

8.5 

8.0 

8.0 

7.5 

6.2 

6.7 

7.1 

5.2 

6.6 

7.5 

5.1 

7.4 

9.2 

7.8 

9.1 

7.3 

7.7 

8.1 

8.1 

7.6 

7.5 

7.1 

7.0 

6.6 

13.5 

2 

14.5 

17.0 

15.5 

17.6 

13.0 

12.0 

11.0 

12.0 

14.0 

11.6 

10.0 

llA 

11.0 

11.6 

9.5 

11.5 

13.5 

14  5 

16.0 

13.5 

14.5 

17.0 

IAS 

17.2 

12.8 

11.7 

10.7 

11.7 

13.6 

li.i 

9.6 

11.0 

10.5 

11.0 

9.0 

10.8 

12.7 

13.6 

14.0 

Table  F. — Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade — Continued 


321 


Group. 

310-301 

B.C. 

320-11 

330-21 

340-31 

1 

in 

•n 

360-51 

1 

tn 

380-71 

390-81 

1 

400-391 

410-401 

420-11 

cs 

1 - 

440-31 

450-41 

to 

470-61 

i 

00 

490-81 

500-491 

21,  Total  growth . 

145.5 
12 
46.0 

552.5 
24 

207.0 

219.5 
11 

90.0 

31.0 

2 

14.3 

68.0 

4 

34.7 
56.0 

5 

34.8 
15.0 

2 

10.8 
10.0 

1 

8.8 

7.0 

1 

6.1 

13.0 

2 

12.0 

144.0 

11 

44.7 

530.0 

153.5 

11 

46.5 

529.0 

97.5 

7 

29.7 

534.6 

76.0 

7 

22.2 

543.6 

84.0 

5 

24.4 

583.5 

106.0 

6 

29.3 

606.5 

22.  Total  growth . 

644.5 

563.6 

616.6 

24 

204.0 

239.5 

695.5 
23 

197.0 

240.6 

491.0 

19 

161.0 

185.0 

422.0 

16 

137.0 

184.0 

337.0 

13 

106.5 

187.0 

351.5 
13 

109.0 

169.5 

318.0 

12 

93.2 

165.6 

154.5 
8 

44.6 

146.5 
11 
50.1 
38.0 

131.5 

4 

37.0 

101.0 

9 

35.2 

28.0 

Corrected  growth . 

23.  Total  growth . 

196.0 

223.0 

193.5 

228.5 

194.0 

256.0 

195.0 

228.0 

207.0 

198.0 

212.0 

190.0 

222.0 

218.0 

190.5 

228.0 

108.5 

9 

37.1 

19.0 

149.0 

9 

50.0 

18.0 

Corrected  growth . 

24.  Total  growth. . . . 

90.2 

32.0 

92.0 

36.0 

102.0 

38.0 

89.8 

38.0 

77.2 

38.0 

73.4 

28.0 

83.2 

30.0 

86.5 

32.0 

89.5 

44.0 

89.3 

40.0 

67.8 

28.0 

efb 

42.0 

67.3 

30.0 

60.0 

30.0 

57.6 

38.0 

Corrected  growth . 

25.  Total  growth . 

14.6 

52.6 

16.3 

51.6 

17.0 

43.0 

16.8 

47.6 

16.7 

66.0 

12.1 

62.6 

12.9 

57.0 

13.6 

47.0 

18.5 

49.0 

16.6 

56.0 

15.6 

61.0 

17.0 

58.5 

12.1 

63.5 

12.0 

41.0 

15.0 

41.5 

14.9 

47.0 

10.8 

61.5 

7.3 

64.0 

6.8 

61.5 

Corrected  growth . 

26.  Total  growth . 

26.5 

53.0 

25.8 

64.5 

21.4 

66.0 

23.4 

68.0 

27.4 

73.0 

30.2 

66.0 

27.2 

77.0 

22.1 

78.0 

22.8 

80.5 

25.8 

88.0 

27.8 

83.5 

26.3 

71.5 

23.8 

95.0 

18.0 

101.0 

18.1 

90.0 

20.3 

97.0 

22.0 

97.5 

27.1 

93.5 

25.6 

100.0 

Corrected  growth . 

27.  Total  growth . 

35.6 

14.0 

39.0 

12.5 

38.8 

14.5 

40.2 

18.5 

42.6 

20.5 

38.0 

19.5 

43.8 

20.0 

44.1 

26.5 

45.0 

22.0 

48.6 

21.0 

45.6 

21.0 

38.6 

22.0 

50.5 

20.0 

53.0 

23.0 

46.7 

24.0 

49.7 

26.0 

49.5 

22.0 

47.1 

22.0 

49.9 

18.0 

Corrected  growth . 

f  28  Total  growth . 

9.9 

11.6 

8.8 

13.6 

io.o 

10.0 

12.6 

7.0 

13.8 

6.6 

12.9 

6.0 

13.1 

7.0 

17.1 

7.6 

14.0 

6.0 

13.2 

7.0 

13.0 

8.0 

13.6 

7.6 

12.1 

9.0 

13.7 

9.5 

14.2 

10.5 

15.2 

10.5 

12.7 

9.0 

12.6 

11.0 

10.2 

13.0 

(  29.  Corrected  growth . 

30.  Total  growth . 

10.0 

8.5 

11.7 

9.0 

8.7 

12.0 

6.0 

12.0 

4.7 

10.5 

6.1 

11.0 

6.0 

8.0 

6.4 

11.0 

6.1 

14.0 

6.9 

15.0 

6.7 

17.0 

6.2 

18.0 

7.4 

19.0 

7.7 

17.0 

8.4 

16.0 

8.3 

14.0 

7.0 

14.5 

8.5 

12.0 

10.0 

U.5 

Corrected  growth . 

31.  Total  growth . . 

7.4 

13.0 

7.8 

13.0 

10.3 

15.5 

io.3 

17.0 

9.0 

16.0 

9.4 

15.5 

6.8 

15.5 

9.3 

15.0 

11.8 

13.0 

12.5 

12.0 

14.1 

14.0 

14.8 

14.5 

16.6 

16.0 

13.6 

25.5 

12.7 

15.0 

11.0 

13.0 

11.3 

17.0 

9.2 

18.5 

8.7 

12.5 

Corrected  growth . 

12.0 

11.9 

14.1 

15.4 

13.6 

13.9 

13.9 

13.4 

11.5 

10.6 

12.3 

12.7 

14.0 

22.1 

13.0 

11.2 

14.6 

15.8 

10.7 

Group. 

So 

2« 

in 

1*4 

<j> 

M 

lO 

1 

v> 

i 

1 

in 

in 

in 

i 

1 

in 

i 

v> 

Ot 

•H 

2 

tn 

i 

o 

t 

in 

o 

I 

o 

1 

o 

o 

00 

<!, 

Oi 

o 

o 

113.0 

7 

38.0 

24.0 

2 

9.0 

50.5 

4 

20.9 

86.5 

5 

42.9 
17.0 

2 

9.6 

12.0 

1 

9.1 

15.0 

1 

11.2 

12.5 

2 

10.6 

123.0 

7 

40.3 

17.0 

77.5 

6 

26.0 

20.0 

80.5 

6 

26.4 

11.0 

90.0 

5 

28.9 

10.0 

109.6 

6 

34.2 

9.0 

111.6 

6 

43.4 

11.0 

84.0 

4 

24.0 

12.0 

Corrected  growth . 

9.0 

11.0 

16.0 

20.0 

42.0 

2 

12.2 

23.0 

No.  of  measurements . 

Corrected  growth . 

25.  Total  growth . 

6.3 

49.0 

7.4 

67.6 

4.0 

59.5 

8.6 

63.0 

4 

25.1 

90.0 

3.2 

33.0 

2 

13.0 

96.5 

3.8 

33.0 

4.1 

15.0 

3.0 

18.6 

3.6 

16.6 

6.1 

18.0 

6.1 

26.0 

26.0 

22.0 

26.0 

27.0 

35.0 

43.0 

44.5 

2 

13.8 

84.0 

Corrected  growth . 

26.  Total  growth . 

20.1 

86.6 

23.3 

105.0 

23.8 

84.0 

12.9 

96.0 

5.8 

110.0 

7.1 

105.6 

6.9 

88.0 

6.7 

104.5 

9.6 

106.6 

8.4 

100.0 

9.3 

92.0 

7.7 

100.0 

9.0 

109.0 

9.1 

126.0 

11.5 

122.0 

13.7 

108.0 

Corrected  growth . 

27.  Total  growth . 

No.  of  measurements . 

41.8 

20.0 

50.8 

18.0 

40.0 

13.0 

42.3 

22.0 

44.4 

16.0 

44.3 

18.0 

60.2 

19.0 

47.6 

22.0 

39.3 

16.0 

46.0 

19.0 

46.7 

19.0 

43.2 

18.0 

39.4 

24.0 

42.3 

20.0 

45.6 

18.0 

52.3 

25.0 

60.1 

17.0 

43.9 

19.0 

33.9 

14.0 

Corrected  growth . 

(  28  Total  growth . 

<  &  No.  of  measurements . 

11.0 

14.0 

9.8 

16.0 

7.0 

15.6 

11.7 

13.5 

7.9 

12.5 

9.3 

12.6 

9.7 

12.0 

11.2 

12.0 

8.1 

9.5 

9.5 

10.5 

9.4 

10.5 

8.8 

13.6 

il.7 

13.0 

9.5 

13.0 

8.6 

12.0 

11.7 

15.0 

7.8 

14.0 

8.6 

12.0 

6.3 

18.0 

1  29.  Corrected  growth . 

30.  Total  growth . 

No.  of  measurements. .... 

10.6 

13.0 

11.8 

10.0 

11.3 

9.0 

9.6 

8.0 

8.9 

11.0 

8.7 

12.0 

8.3 

15.0 

8.2 

15.0 

6.4 

14.5 

7.0 

12.0 

6.9 

12.0 

8.6 

12.5 

8.3 

15.0 

8.2 

19.0 

7.5 

14.0 

9.2 

16.0 

8.5 

15.0 

7.2 

13.0 

10.6 

14.0 

Corrected  growth . 

31.  Total  growth . 

No.  of  measurements. .... 

9.6 

17.0 

7.3 

20.0 

6.5 

19.0 

5.7 

20.0 

7.7 

15.5 

8.3 

14.0 

10.2 

20.0 

10.1 

11.5 

9.6 

13.0 

7.8 

12.0 

7.8 

16.0 

8.0 

17.0 

9.4 

16.5 

11.8 

13.5 

8.6 

14.0 

9.7 

14.5 

9.0 

21.0 

7.7 

19.0 

8.2 

18.0 

Corrected  growth . 

14.4 

16.8 

15.9 

16.6 

12.7 

11.4 

16.0 

9.1 

10.2 

9.3 

11.5 

12.9 

12.4 

10.0  1  10.2 

10.4 

15.0 

13.3 

12.5 

22 


322  Table  F. — Growth  of  Sequoia  washingtoniana  by  Groups  for  each  Decade — Continued. 


Group. 

710-701 

B.C. 

720-11 

i 

740-31 

*■4 

1 

760-Sl  I 

i 

780-71 

800-791 

I08-0I8 

820-11 

830-21 

840-31 

850-41 

860-51 

870-61 

880-71 

18-068 

900-891 

53.5 

2 

16.7 

79.5 

6 

31.7 
20.0 

2 

8.8 

18.0 

1 

10.5 
11.0 

1 

6.3 

19.0 

2 

13.0 

No.  of  measurements. 

2G.  Total  growth . 

No.  of  measurements. 
Corrected  growth . . , . 

27.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . . 

(  28  Total  growth . 

t  &  No.  of  measurements 
(  29.  Corrected  growth. . . 

30.  Total  growth . 

No.  of  measurements 
Corrected  growth. . . 

31.  Total  growth . 

No.  of  measurements 
Corrected  growth. . . 

71.0 

80.5 

87.5 

94.5 

83.0 

81.0 

63.0 

64.0 

55.0 

67.5 

91.5 

98.0 

110.6 

5 

36.8 

18.0 

67.0 

3 

21.9 

16.0 

61.0 

3 

16.0 

24.0 

57.0 

3 

17.0 

27.0 

. 

. 

. 

28.2 

13.0 

31.6 

11.0 

33.8 

17.0 

36.2 

14.0 

31.5 

25.0 

^.4 

17.0 

23.3 

18.0 

23.2 

88.0 

19.6 

40.0 

23.6 

24.0 

31.2 

30.0 

32.7 

26.0 

28.0 

26.0 

26.0 

6.7 

24.0 

4.7 

33.0 

7.3 

37.0 

5.9 

39.0 

10.5 

10.0 

7.1 

10.0 

7.4 

22.0 

15.6 

19.0 

16.1 

21.0 

9.5 

19.0 

11.9 

18.0 

10.3 

17.0 

7.0 

15.0 

5.7 

20.0 

9.1 

23.0 

10.1 

16.0 

10.3 

15.0 

0.5 

24.0 

9.3 

28.0 

13.8 

13.0 

18.8 

16.5 

20.9 

15.0 

21.8 

14.5 

10.5 

15.0 

10.4 

15.0 

11.9 

13.0 

10.2 

15.0 

11.0 

18.0 

9.9 

20.0 

9.2 

16.0 

8.7 

20.0 

7.5 

23.0 

10.0 

16.0 

11.4 

15.0 

fs 

16.0 

7.3 

18.0 

il.4 

16.0 

13.2 

18.0 

7.4 

17.0 

8.8 

14.0 

8.4 

15.0 

8.0 

19.0 

8.2 

14.5 

8.1 

16.0 

6.9 

20.6 

7.9 

18.0 

9.4 

16.0 

10.3 

17.0 

8.1 

20.0 

10.1 

19.0 

11.6 

24.0 

7.9 

24.0 

7.3 

27.0 

7.7 

21.0 

8.6 

23.0 

7.5 

16.0 

8.4 

21.6 

11.4 

9.3 

9.8 

12.3 

8.9 

io.i 

12.7 

ii.b 

9.7 

10.1 

il.8 

ii.i 

13.8 

13.7 

15.3 

11.8 

12.7 

8.7 

il.6 

Group. 

i 

o> 

i 

1 

i 

i 

i 

is 

2§ 

•N 

i 

•M 

i 

Pi4 

1 

o 

*4 

i 

m4 

i 

m4 

i 

i| 

8.0 

2 

2.8 

29.0 

1 

13.4 
29.0 

1 

13.5 
20.0 

2 

10.6 

12.0 

13.0 

16.0 

25.0 

-30.0 

No.  of  measurements 

2 

0.0 

13.0 

4.1 

17.0 

4.4 

18.0 

6.2 

20.0 

7.8 

14.0 

(  28  Total  growth . 

1  A  No.  of  measurements 
(  29.  Corrected  growth . . .' 

30.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . 

31.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . 

22.0 

18.0 

18.0 

17.0 

20.0 

20.0 

22.0 

14.0 

19.0 

19.0 

1 

7.4 

12.6 

7.0 

1 

6.6 

11.5 

7.8 

22.0 

8.2 

26.0 

8.9 

27.0 

6.1 

41.0 

5.6 

37.0 

0.4 

25.0 

7.6 

18.0 

7.5 

11.6 

7.1 

9.6 

8.2 

10.6 

8.2 

11.5 

8.9 

12.0 

6.6 

15.0 

7.6 

11.5 

8.5 

7.0 

26.0 

1 

9.8 

45.0 

2 

19.3 

10.1 

22.5 

11.8 

24.5 

12.3 

22.5 

18.2 

23.5 

16.2 

27.5 

10.8 

24.0 

7.7 

27.0 

4.9 

27.5 

4.0 

28.0 

4.4 

29.5 

4.7 

26.0 

4.9 

34.5 

6.1 

37.0 

4.6 

32.0 

4.9 

38.0 

4.5 

34.0 

3.3 

36.0 

2.7 

39.0 

11.8 

12.7 

11.5 

12.0 

13.8 

12.0 

13.4 

13.5 

13.5 

14.0 

12.3 

16.1 

ILO 

14.6 

1^2 

is.i 

15.8 

16.9 

Group. 

,  O 

6PQ 

So 

p4 

<i> 

p4 

1 

W4 

1 

1 

sM 

sM 

i 

1 

*•4 

1 

i 

is 

a- 

<i>e 

S2 

1 

1 

*4 

i 

P4 

i 

1 

M 

i 

94 

*4 

JL 

5  Ok 

is 

•<4  ” 

30.  Total  growth . 

23.0 

1 

8.6 

48.0 

2 

20.3 

No.  of  measurements 
Corrected  growth . . . 

31.  Total  growth . 

No.  of  measurements 
Corrected  growth . . . 

33.0 

50.0 

48.0 

54.5 

73.0 

50.6 

60.5 

69.5 

67.0 

32.0 

8.5 

8.0 

12.5 

11.0 

16.5 

18.5 

21.5 

24.5 

32.0 

42.0 

2 

13.1 

13.8 

20.8 

19.7 

22.2 

29.5 

W.l 

23.9 

23.3 

26.0 

12.2 

3.2 

3.0 

4.6 

4.0 

5.9 

6.5 

7.3 

8.1 

10.4 

The  first  line  in  each  group  in  Table  F  indicates  the  sum  of  all  the  measurements  of  growth  included  in  the 
group.  The  second  line  indicates  the  number  of  measurements.  The  third  line  indicates  the  total  growth  cor¬ 
rected  for  age  and  longevity  accordmg  to  Table  E.  The  average  growth,  corrected  or  uncorrected,  is  obtained  by 
dividing  the  figures  in  the  first  or  third  lines,  respectively,  by  those  in  the  second  line. 


Table  G. — Summary  of  Growth  of  Sequoia  washingtoniana.  Trees  measured  in  1911  and  1912.  323 

By  Groups,  corrected  and  uncorrected,  including  Caspian  Factor. 

When  the  number  of  measurements  is  not  indicated  in  column  C,  it  is  the  same  as  the  figiues  next  above  or  below. 


(A) 

Date  of 
decade. 

Total  imcor-  q 
reeled  growth.  ” 

No.  of  meas- 
urements. 

Average  unoor-^ 
reeled  growth.  O 
See  fig.  38. 

Total  cor-  o 

rected  growth. 

(F) 

ill 

(G) 

1° 

tl 

Final  cor¬ 

rected  average  ^ 
per  Caspian.  04 

See  figs.  50  ^ 

and  72. 

•  Mean  of 

three  decades. 

(A) 

Date  of 
decade. 

(B) 

J  ^ 

’a  V 

ts 

Hg 

(C) 

as 

■g  0 

a 

1  = 

Average  un-  ^ 

corrected  0 

growth. 

(E) 

i| 

O  s 

(F) 

ki 

4)  « 

<  g 

Caspian  ■g 

factor.  w 

Final  cor- 

rected  average  w 

per  Caspian. 

(I) 

m 

a> 

o 

u 

♦  g 

1901-1910 

573.5 

44 

(13.01) 

(351.5) 

(7.99) 

90.0 

(7.11) 

1091-1100 

8124.6 

659 

12.33 

4416.5 

6.70 

98.1 

6.57 

1891-1900 

5404.5 

531 

(10.18) 

(4358.4) 

(8.21) 

90.1 

(7.40) 

— 

1081-1090 

8268.5 

659 

12.68 

4524.5 

6.86 

98.2 

6.74 

— 

1881-1890 

7522.5 

748 

10.06 

5820.5 

7.77 

90.2 

7.00 

— 

1071-1080 

8228.5 

659 

12.50 

4521.0 

6.85 

98.3 

6.74 

— 

1871-1880 

7760.0 

782 

9.91 

5850.6 

7.49 

90.3 

6.75 

— 

1061-1070 

8106.5 

668 

12.31 

4326.9 

6.67 

98.4 

6.46 

— 

1801-1870 

7522.0 

784 

9.60 

5737.4 

7.30 

90.4 

6.60 

— 

1061-1060 

8265.5 

655 

12.62 

4389.2 

6.70 

98.5 

6.60 

— 

1851-1860 

7624.0 

785 

9.70 

6765.2 

7.35 

90.5 

6.65 

— 

1041-1060 

8567.0 

655 

13.08 

4526.1 

6.91 

98.6 

6.82 

— 

1841-1850 

7455.5 

9.50 

6670.0 

7.21 

90.6 

6.63 

— 

1031-1040 

8723.5 

653 

13.37 

4599.5 

7.05 

98.7 

6.96 

— 

1831-1840 

7629.0 

. 

9.58 

5689.0 

7.24 

90.7 

6.56 

— 

1021-1030 

9188.5 

651 

14.10 

4796.7 

7.37 

98.8 

7.28 

— 

1821-1830 

7393.5 

9.41 

5683.5 

7.23 

90.8 

6.56 

— 

1011-1020 

9384.0 

649 

14.47 

4817.6 

7.42 

98.9 

7.34 

— 

1811-1820 

7687.6 

9.78 

5783.5 

7.36 

00.9 

6.68 

— 

1001-1010 

9607.0 

647 

14.87 

4863.5 

7.62 

99.0 

7.46 

1801-1810 

7745.5 

9.86 

6003.7 

7.61 

91.0 

6.83 

— 

991-1000 

9079.0 

644 

14.10 

4578.8 

7.11 

99.1 

7.05 

— 

1791-1800 

7716.0 

9.83 

6714.3 

7.27 

91.1 

6.62 

— 

981-990 

8638.6 

644 

13.40 

4356.6 

6.77 

99.2 

6.71 

— 

1781-1790 

7560.6 

7756.0 

9.62 

5541.2 

7.06 

01.2 

6.42 

— 

971-980 

8488.0 

644 

13.17 

4262.9 

6.62 

99.3 

6.67 

1771-1780 

7661.6 

9.88 

5689.7 

7.24 

91.3 

6.60 

— 

961-970 

8333.0 

640 

13.02 

4174.6 

6.52 

99.4 

6.48 

— 

1761-1770 

7891.5 

9.76 

6562.4 

7.08 

01.4 

6.47 

— 

961-960 

8471.5 

640 

13.22 

4187.6 

6.54 

99.5 

6A0 

1751-1760 

8099.6 

10.03 

5802.0 

7.38 

91.5 

6.75 

— 

941-950 

8406.0 

637 

13.20 

4121.8 

6.46 

90.6 

6.43 

1741-1750 

8112.6 

10.30 

5905.5 

7.61 

01.6 

6.88 

— 

931-940 

8568.5 

633 

13.53 

4180.5 

6.60 

99.7 

6.58 

— 

1731-1740 

8079A 

10.32 

6787.6 

7.36 

91.7 

6.75 

— 

921-930 

8765.6 

630 

13.90 

4258.3 

0.76 

99.8 

6.75 

— 

1721-1730 

7992.6 

10.29 

5662.7 

7.20 

01.8 

6.61 

— 

911-920 

8795.0 

624 

14.08 

4271.9 

6.83 

99.9 

6S2 

— 

1711-1720 

7913.0 

10.18 

6634.2 

7.17 

91.0 

6.58 

— 

901-910 

8803.0 

620 

14.21 

4254.8 

6.86 

100.0 

6.86 

— 

1701-1710 

7913.0 

10.08 

5560.1 

7.07 

02.0 

6.61 

— 

891-900 

8727.6 

612 

14.27 

4172.4 

6.82 

100.0 

6.82 

1691-1700 

8198.5 

10.42 

5762.6 

7.32 

02.1 

6.73 

881-890 

8367.5 

607 

13.80 

4002.2 

6.60 

100.0 

6.60 

1081-1690 

8342.0 

786 

10.64 

6940.8 

7.66 

92.2 

6.06 

871-880 

8112.6 

605 

13.41 

3774.7 

6.24 

100.0 

624 

— 

1671-1680 

8356.0 

784 

10.67 

5797.6 

7.39 

92.3 

6.82 

— 

861-870 

8120.5 

599 

13.63 

3847.9 

6.42 

100.0 

6.42 

— 

1661-1670 

8256.0 

783 

10.55 

5760.0 

7.35 

92.4 

6.78 

— 

851-860 

8150.0 

595 

13.70 

3740.4 

6.28 

100.0 

6.28 

— 

1651-1660 

8210.0 

783 

10.49 

5686.2 

7.26 

92.5 

6.71 

— 

841-860 

8220.5 

595 

13.80 

3820.8 

6.42 

100.0 

6.42 

— 

1641-1050 

8303.6 

782 

10.62 

5706.6 

7.30 

92.6 

6.75 

— 

831-840 

8176.6 

690 

13.85 

3807.7 

6.45 

100.0 

6.45 

— 

1631-1640 

8227.0 

778 

10.56 

6671.6 

7.28 

92.7 

6.74 

— 

821-830 

8060.0 

589 

13.70 

3734.4 

6.34 

100.0 

6.34 

— 

1021-1630 

8360.5 

10.73 

6713.9 

7.34 

02.8 

6.81 

— 

811-820 

8219.0 

586 

14.03 

3761.6 

6.40 

100.0 

6.40 

— 

1611-1620 

8448.0 

10.84 

6730.7 

7.36 

02.0 

6.83 

801-810 

7963.0 

578 

13.77 

3687.3 

6.38 

100.0 

6.38 

— 

1601-1610 

8321.0 

778 

10.69 

5700.4 

7.33 

03.0 

6.81 

— 

791-800 

8171.0 

576 

14.20 

3741.6 

6.50 

100.0 

6.50 

— 

1591-1600 

8171.0 

777 

10.52 

5526.4 

7.11 

93.1 

6.62 

781-790 

8136.5 

576 

14.11 

3673.7 

6.38 

100.0 

6.38 

— 

1581-1590 

8260.0 

777 

10.62 

5558.9 

7.16 

03.2 

6.67 

_ 

771-780 

7760.0 

558 

13.90 

3530.6 

6.32 

100.0 

6.32 

— 

1571-1580 

8335.0 

775 

10.78 

6573.8 

7.19 

03.3 

6.70 

— 

761-770 

7271.0 

558 

13.04 

3383.7 

6.00 

100.0 

6.06 

— 

1561-1570 

8551.5 

775 

11.03 

5640.6 

7.28 

03.4 

6.80 

— 

751-760 

7605.6 

556 

13.70 

3509.6 

6.31 

100.0 

6.31 

— 

1551-1560 

8402.5 

774 

10.86 

6604.6 

7.24 

93.5 

6.77 

_ 

741-750 

7780.0 

552 

14.11 

3458.0 

6.26 

100.0 

6.26 

— 

1541-1550 

8371.5 

773 

10.82 

5472.0 

7.08 

93.6 

6.62 

— 

731-740 

7778.0 

552 

14.11 

3400.4 

6.17 

100.0 

6.17 

— 

1531-1540 

8422.6 

773 

10.90 

5448.6 

7.04 

93.7 

6.59 

— 

721-730 

7442.6 

545 

13.63 

3330.3 

6.11 

100.0 

6.11 

— 

1521-1530 

8371.5 

772 

10.86 

5372.4 

6.95 

93.8 

6.52 

_ 

711-720 

7781.5 

543 

14.32 

3307.8 

6.08 

100.0 

6.08 

— 

1511-1620 

8405.0 

772 

10.90 

6356.3 

6.93 

93.9 

6.61 

_ 

701-710 

7625.0 

537 

14.21 

3361.9 

6.26 

100.0 

6.26 

— 

1501-1610 

8124.0 

770 

10.55 

5114.0 

6.65 

94.0 

6.25 

_ 

691-700 

7526.0 

627 

14.30 

3319.6 

6.30 

10.00 

6.30 

— 

1491-1500 

7853.5 

766 

10.27 

5019.6 

6.66 

04.1 

6.17 

_ 

681-690 

7349.0 

518 

14.18 

3269.9 

6.30 

100.0 

6.30 

— 

1481-1490 

7840.0 

765 

10.23 

4944.3 

6.46 

94.2 

6.08 

_ 

671-680 

7290.5 

617 

14.10 

3237.7 

6.25 

100.0 

6.25 

— 

1471-1480 

7749.5 

763 

10.14 

4888.2 

6.41 

94.3 

6.04 

_ 

661-670 

7156.0 

511 

14.01 

3154.0 

6.17 

100.0 

6.17 

— 

1461-1470 

7877.0 

759 

10.38 

4021.6 

6.47 

94.4 

6.10 

_ 

651-660 

7074.6 

504 

14.03 

3101.2 

6.15 

100.0 

6.15 

— 

1461-1460 

8203.5 

10.81 

5258.3 

6.93 

94.5 

6.55 

641-650 

6918.5 

499 

13.88 

3029.1 

6.07 

100.0 

6.07 

— 

1441-1450 

85.55.0 

11.28 

5235.2 

6.89 

94.6 

6.51 

— 

631-6401 

6943.0 

489 

14.18 

3057.8 

6.24 

100.0 

6.24 

— 

1431-1440 

8709.5 

11.49 

5260.2 

6.92 

94.7 

6.54 

_ 

621-630 

6852.0 

483 

14.18 

3008.6 

6.22 

100.0 

6.22 

— 

1421-1430 

8831.5 

759 

11.67 

5252.7 

6.92 

94.8 

6.55 

_ 

611-620 

7179.0 

471 

15.28 

3114.7 

6.60 

100.0 

6.60 

— 

1411-1420 

9047.5 

757 

11.98 

5326.2 

7.04 

94.9 

6.68 

_ 

601-610 

6999.0 

460 

16.20 

3138.3 

6.81 

100.0 

6.81 

— 

1401-1410 

9070.0 

766 

12.02 

5312.0 

7.04 

95.0 

6.69 

— 

691-600 

6698.0 

451 

14.85 

3041.6 

6.75 

100.0 

6.75 

— 

1391-1400 

9206.0 

12.20 

5324.6 

7.05 

95.1 

6.70 

681-690 

6493.0 

442 

14.70 

2932.2 

6.64 

100.0 

6.64 

— 

1381-1390 

9546.0 

755 

12.62 

6478.1 

7.25 

95.2 

6.89 

_ 

671-580 

6517.0 

436 

15.00 

2883.1 

6.63 

100.0 

6.63 

— 

1371-1380 

9936.0 

762 

13.20 

5570.9 

7.41 

95.3 

7.06 

_ 

661-570 

6282.5 

429 

14.65 

2785.2 

6.48 

100.0 

6.48 

— 

1361-1370 

9945.5 

762 

13.22 

5538.7 

7.27 

95.4 

6.93 

551-560 

5999.5 

425 

14.12 

2676.0 

6.29 

100.0 

6.29 

— 

1351-1360 

9900.5 

742 

13.35 

5529.1 

7.45 

95.5 

7.12 

_ 

641-560 

6245.5 

422 

14.81 

2773.7 

6.58 

100.0 

6.58 

— 

1341-1350 

10121.0 

736 

13.76 

5646.5 

7.66 

05.6 

7.32 

631-640 

5762.0 

411 

14.02 

2623.6 

6.38 

100.0 

6.38 

— 

1331-1340 

9975.0 

726 

13.73 

5631.9 

7.76 

96.7 

7.41 

621-530 

6794.0 

409 

14.17 

2642.2 

6.46 

100.0 

6.46 

— 

1321-1330 

8796.0 

704 

12.50 

5201.8 

7.39 

05.8 

7.08 

_ 

511-520 

6773.6 

404 

14.30 

2603.8 

6.44 

100.0 

6.44 

— 

1311-1320 

8354.0 

697 

12.00 

5034.6 

7.23 

95.0 

6.93 

_ 

501-510 

6700.5 

402 

14.22 

2593.6 

6.45 

100.0 

6.45 

1301-1310 

7687.5 

695 

11.05 

4630.2 

6.67 

06.0 

6.40 

_ 

491-500 

5644.0 

397 

14.22 

2526.9 

6.36 

100.0 

6.36 

— 

1291-1300 

7359.6 

690 

10.68 

4535.8 

6.67 

96.1 

6.31 

481-490 

6712.0 

395 

14.46 

2524.9 

6.38 

ibo.o 

6.38 

— 

1281-1290 

7274.6 

690 

10.55 

4492.0 

6.51 

96.2 

6.26 

_ 

471-480 

5782.0 

395 

14.65 

2543.6 

6.44 

100.0 

6.44 

— 

1271-1280 

7257.0 

687 

10.58 

4480.9 

6.53 

96.3 

6.29 

_ 

461-470 

5620.5 

393 

14.30 

2477.9 

6.30 

100.0 

6.30 

— 

1261-1270 

7366.0 

685 

10.76 

4526.3 

6.60 

96.4 

6.36 

_ 

451-460 

6562.5 

387 

14.35 

2433.5 

6.28 

100.0 

6.28 

— 

1261-1260 

7383.0 

685 

10.78 

4519.4 

6.69 

96.5 

6.30 

_ 

441-450 

5488.0 

381 

14.40 

2395.4 

6.29 

100.0 

6.29 

— 

1241-1260 

7406.0 

682 

10.86 

4509.2 

6.61 

96.6 

6.38 

_ 

431-440 

5192.5 

367 

14.13 

2317.6 

6.31 

100.0 

6.31 

— 

1231-1240 

7417.0 

682 

10.87 

4481.8 

6.57 

96.7 

6.35 

_ 

421-430 

6292.6 

362 

14.61 

2344.1 

6.48 

100.0 

6.48 

— 

1221-1230 

7787.6 

680 

11.45 

4619.6 

6.80 

96.8 

6.58 

411-420 

4819.0 

350 

13.73 

2201.7 

6.29 

100.0 

6.29 

— 

1211-1220 

7598.5 

676 

11.24 

4497.6 

6.65 

96.9 

6.44 

401-410 

4937.0 

350 

14.11 

2236.0 

6.38 

100.0 

6.38 

— 

1201-1210 

7495.5 

672 

11.16 

4487.5 

6.68 

97.0 

6.47 

_ 

391-400 

4922.4 

848 

14.15 

2313.3 

6.65 

100.2 

6.66 

— 

1191-1200 

7793.0 

672 

11.16 

4450.2 

6.63 

97.1 

6.43 

_ 

381-390 

4959.6 

344 

14.42 

2234.5 

6.48 

100.4 

6.50 

— • 

1181-1190 

7287.0 

670 

10.89 

4296.3 

6.41 

97.2 

6.22 

_ 

371-380 

6005.0 

336 

14.90 

2262.5 

6.74 

100.6 

6.78 

— 

1171-1180 

7455.0 

669 

11.16 

4341.8 

6.48 

97.3 

6.30 

361-370 

4607.6 

326 

15.07 

2187.9 

6.71 

100.8 

6.76 

— 

1161-1170 

7376.5 

669 

11.02 

4249.2 

6.35 

97.4 

6.18 

— 

351-360 

4847.6 

321 

1.5.10 

2164.9 

6.75 

101.0 

6.82 

— 

1151-1160 

7347.0 

667 

11.02 

4214.8 

6.32 

97.6 

6.16 

— 

341-360 

4772.6 

317 

15.05 

2111.9 

6.65 

101.2 

6.73 

— 

1141-1150 

7555.5 

667 

11.32. 

4276.8 

6.42 

97.6 

6.27 

— 

331-340 

4746.5 

311 

15.25 

2108.5 

6.77 

101.4 

6.87 

— 

1131-1140 

7866.0 

665 

11.82 

4307.5 

6.61 

97.7 

6.45 

— 

321-330 

4786.0 

309 

15.50 

2082.0 

6.74 

101.6 

6.83 

— 

1121-1130 

7937.5 

662 

12.00 

4432.0 

6.69 

97.8 

6.54 

— 

311-320 

4670.0 

306 

14.92 

2089.0 

6.82 

101.8 

6.95 

— 

1111-1120 

7985.0 

659 

12.12 

4420.1 

6.70 

97.9 

6.55 

— 

301-310 

4546.0 

295 

15.40 

2015.4 

6.82 

102.0 

6.96 

— 

1101-1110 

7975.0 

12.10 

4386.6 

6.65 

98.0 

6.51 

— 

291-300 

4577.0 

294 

15.58 

1992.2 

6.78 

102.2 

6.94 

— 

three  decades. 


324  Table  G. — Summary  of  Growth  of  Sequoia  wa^ingtoniana.  Trees  measured  in  1911  and  1912. 

By  Groups,  corrected  and  uncorrected,  including  Caspian  Factor — Continued. 

When  the  number  of  measurements  is  not  indicated  in  column  C,  it  is  the  same  as  the  figures  next  above  or  below. 


(A) 

Date  of 
decade. 

Total  uncor-  -g 
rected  growth. 

i 

1 

(C 

<)> 

S  ji 

£  a 

a> 

•s  a 

•  g 

Z 

Average  un-  ^ 

corrected  0 

growth.  ^ 

Total  cor-  Q 

reeled  growth. 

Average  cor-  G 

rccted  growth. 

Caspian  •g 

factor. 

Final  cor-  ^ 

rected  average  ^ 

per  Caspian. 

♦  Mean  of  ,-5 

three  decades. 

(A) 

Date  of 
decade. 

Total  uncor-  q 

rected  growth,  w 

(C) 

tf) 

0  id 

i  ^ 
a 

Average  un- 

oorreoted  g 

growth. 

Total  cor¬ 

rected  growth,  ■g 

Average  cor-  g 

rected  growth.  ^ 

Caspian  0 

factor. 

Final  cor¬ 

rected  average  '5 
per  Caspian. 

*  Mean  of  .3 

three  decades. 

281-290 

4527.0 

292 

15.50 

1975.1 

6.76 

102.4 

6.92 

__ 

520-511 

338.5 

24 

14.10 

144.0 

6.00 

115.0 

6.90 

7.39 

271-280 

4591.0 

286 

16.05 

1975.3 

6.90 

102.6 

7.08 

— 

530-521 

324.0 

22 

14.72 

153.2 

6.97 

115.0 

8.01 

7.32 

201-270 

4676.0 

284 

16.47 

1998.4 

7.03 

102.8 

7.23 

— 

540-531 

291.5 

22 

13.24 

134.9 

6.13 

115.0 

7.05 

7.61 

251-260 

4571.0 

283 

16.15 

1960.6 

6.93 

103.0 

7.14 

— 

550-541 

316.5 

22 

14.40 

148.3 

6.75 

115.0 

7.76 

7.47 

241-250 

4601.5 

280 

16.42 

1956.1 

6.97 

103.2 

7.19 

— 

560-551 

305.0 

20 

15.25 

132.3 

6.62 

115.0 

7.61 

7.81 

231-240 

4479.0 

272 

16.50 

1913.4 

7.04 

103.4 

7.28 

— 

570-561 

308.0 

20 

15.40 

142.1 

7.11 

115.0 

8.17 

7.81 

221-230 

4497.0 

265 

16.98 

1915.5 

7.22 

103.6 

7.49 

— 

580-571 

287.0 

19 

15.10 

128.3 

6.75 

115.0 

7.76 

7.77 

211-220 

4416.0 

260 

17.00 

1863.4 

7.16 

103.8 

7.43 

— 

590-581 

193.5 

15 

12.90 

96.3 

6.42 

115.0 

7.38 

7.17 

201-210 

4263.7 

253 

16.85 

1805.4 

7.13 

104.0 

7.42 

— 

600-601 

167.5 

12.50 

83.1 

6.54 

115.0 

6.37 

6.92 

191-200 

4112.5 

247 

16.67 

1769.1 

7.12 

104.2 

7.42 

— 

610-601 

192.0 

12.80 

91.4 

6.08 

115.0 

7.00 

6.96 

181-190 

3771.0 

239 

15.78 

1615.8 

6.76 

104.4 

7.05 

— 

620-611 

209.0 

13.95 

98.0 

6.54 

n.5.0 

7.51 

7.41 

171-180 

3680.0 

237 

15.53 

1579.4 

6.66 

104.6 

6.97 

— 

630-621 

226.0 

15 

15.08 

102.1 

6.71 

115.0 

7.71 

7.73 

161-170 

3722.5 

235 

15.86 

1586.1 

6.75 

104.8 

7.08 

— 

640-631 

186.5 

13 

14.35 

90.5 

6.93 

115.0 

7.96 

7.86 

151-160 

3682.0 

232 

15.88 

1570.9 

6.77 

105.0 

7.11 

— 

650-641 

187.5 

14.42 

89.5 

6.88 

115.0 

7.90 

7.92 

141-150 

37.50.5 

230 

16.60 

1569.2 

6.81 

105.2 

7.16 

— 

660-651 

193.0 

14.85 

89.4 

6.88 

115.0 

7.90 

8.29 

131-140 

3608.5 

225 

16.05 

1522.1 

6.76 

105.4 

7.12 

— 

670-661 

223.5 

17.20 

102.4 

7.88 

115.0 

9.06 

8.99 

121-130 

3624.5 

222 

16.32 

1518.7 

6.84 

105.6 

7.27 

— 

680-671 

224.0 

17.24 

101.9 

7.84 

115.0 

9.01 

8.81 

111-120 

3563.0 

220 

16.40 

1479.4 

6.72 

105.8 

7.11 

— 

690-681 

214.0 

16.48 

94.4 

7.26 

115.0 

8.35 

8.30 

101-110 

3439.5 

215 

16.00 

1445.5 

6.72 

106.0 

7.12 

— 

700-691 

192.5 

14.80 

85.3 

6.57 

116.0 

7.55 

7.84 

91-100 

3282.0 

209 

15.72 

1384.4 

6.63 

106.2 

7.04 

— 

710-701 

201.0 

13 

15.45 

86.0 

6.62 

115.0 

7.61 

7.37 

81-90 

3296.0 

207 

15.90 

1383.9 

6.68 

106.4 

7.11 

— 

720-711 

138.0 

11 

12.55 

66.5 

6.05 

115.0 

6.96 

7.40 

71-80 

3611.5 

207 

17.50 

1491.2 

7.21 

106.6 

7.68 

— 

730-721 

154.0 

14.00 

73.1 

6.64 

115.0 

7.64 

7.67 

61-70 

3558.5 

203 

17.51 

1456.4 

7.17 

106.8 

7.66 

— 

740-731 

171.5 

15.60 

80.2 

7.30 

116.0 

8.40 

7.95 

61-60 

3432.5 

198 

17.32 

1420.8 

7.18 

107.0 

7.69 

— 

760-741 

181.0 

16.46 

84.2 

7.65 

115.0 

7.80 

7.83 

41-50 

3480.0 

196 

17.77 

1422.2 

7.21 

107.2 

7.73 

— 

760-751 

156.5 

14.22 

69.6 

6.33 

116.0 

7.28 

7.33 

31-40 

3214.0 

184 

17.60 

1330.1 

7.24 

107.4 

7.77 

770-761 

148.0 

13.46 

66.1 

6.00 

115.0 

6.90 

6.90 

21-30 

3120.0 

180 

17.35 

1284.0 

7.14 

107.6 

7.69 

_ 

780-771 

136.5 

12.40 

62.3 

6.67 

115.0 

6.52 

6.84 

11-20 

3117.0 

177 

17.65 

1279.3 

7.22 

107.8 

7.78 

— 

790-781 

154.0 

14.00 

67.8 

6.17 

115.0 

7.10 

6.83 

1-10  A.  D. 

2968.5 

173 

17.17 

1219.0 

7.05 

108.0 

7.61 

— 

800-791 

150.0 

13.63 

65.8 

6.98 

115.0 

6.88 

6.87 

10-1  B.  C. 

2927.0 

173 

16.84 

1188.1 

6.86 

108.2 

7.43 

— 

810-801 

147.5 

13.40 

63.4 

5.76 

115.0 

6.63 

7.02 

20-11 

2918.0 

167 

17.43 

1190.7 

7.14 

108.4 

7.73 

— 

820-811 

175.5 

. 

15.96 

72.2 

6.56 

115.0 

7.65 

7.24 

30-21 

2682.5 

157 

17.10 

1117.0 

7.10 

108.6 

7.71 

— 

830-821 

180.0 

. 

16.38 

72.9 

6.62 

115.0 

7.61 

7.72 

40-31 

2590.6 

154 

16.82 

1076.0 

6.98 

108.8 

7.59 

— 

840-831 

190.5 

11 

17.32 

76.6 

6.96 

115.0 

8.00 

7.72 

60-41 

2652.5 

150 

17.01 

1061.0 

7.08 

109.0 

7.72 

— 

850-841 

142.0 

9 

15.80 

59.2 

6.56 

115.0 

7.55 

7.70 

60-51 

2464.0 

160 

16.42 

1013.8 

6.77 

109.2 

7.40 

— 

860-851 

140.0 

9 

15.56 

59.1 

6.56 

115.0 

7.55 

7.35 

70-61 

2466.6 

150 

16.42 

1004.2 

6.70 

109.4 

7.33 

— 

870-861 

137.0 

9 

15.22 

54.4 

6.04 

115.0 

6.95 

7.31 

80-71 

2479.6 

148 

16.75 

1002.2 

6.77 

109.6 

7.42 

— 

880-871 

84.0 

6 

14.00 

38.9 

6.47 

115.0 

7.44 

7.16 

90-81 

2418.0 

145 

16.68 

982.9 

6.78 

109.8 

7.44 

— 

890-881 

82.0 

13.68 

37.1 

6.17 

115.0 

7.09 

7.56 

100-91 

2360.6 

143 

16.50 

960.5 

6.72 

110.0 

7.39 

— 

900-891 

93.5 

15.58 

43.5 

7.08 

115.0 

8.15 

7.65 

110-101 

2337.0 

141 

16.59 

935.7 

6.64 

110.2 

7.32 

— 

910-901 

86.0 

14.35 

40.3 

6.72 

115.0 

7.72 

7.45 

120-111 

2234.6 

140 

15.95 

868.2 

6.20 

110.4 

6.85 

— 

920-911 

73.5 

12.26 

33.8 

6.62 

115.0 

6.47 

7.10 

130-121 

2172.5 

139 

15.63 

873.4 

6.28 

110.6 

6.95 

— 

930-921 

81.6 

13.60 

37.1 

6.17 

115.0 

7.10 

7.94 

140-131 

2081.0 

137 

15.20 

830.1 

6.07 

110.8 

6.73 

— 

940-931 

85.5 

14.26 

37.9 

6.31 

116.0 

7.26 

7.67 

160-141 

2057.0 

135 

15.22 

818.6 

6.06 

111.0 

6.73 

— 

950-941 

103.6 

17.22 

44.1 

7.34 

115.0 

8.44 

8.07 

160-151 

1996.5 

133 

15.00 

792.6 

5.96 

111.2 

6.63 

— 

960-951 

107.5 

6 

17.90 

44.0 

7.42 

115.0 

8.52 

8.74 

170-161 

2004.0 

131 

15.30 

789.9 

6.02 

111.4 

6.70 

— 

970-961 

71.0 

4 

17.76 

32.2 

8.05 

115.0 

9.25 

8.67 

180-171 

2005.0 

130 

15.42 

78C.1 

6.00 

111.6 

6.70 

— 

980-971 

63.0 

15.75 

28.7 

7.17 

115.0 

8.25 

8.32 

190-181 

1896.0 

125 

15.18 

739.0 

6.91 

111.8 

6.60 

— 

990-981 

67.0 

14.25 

26.9 

6.48 

115.0 

7.45 

7.59 

200-191 

1749.5 

118 

14.80 

692.0 

6.87 

112.0 

6.57 

— 

1000-991 

54.5 

13.62 

24.6 

6.15 

115.0 

7.07 

7.39 

210-201 

1850.0 

118 

15.69 

717.6 

6.08 

112.2 

6.83 

— 

1010-1001 

60.0 

15.00 

26.6 

6.65 

115.0 

7.65 

7.32 

220-211 

1612.5 

112 

14.40 

640.1 

5.72 

112.4 

6.43 

— 

1020-1011 

57.5 

14.37 

25.2 

6.30 

115.0 

7.25 

7.81 

230-221 

1632.5 

105 

15.62 

645.3 

6.15 

112.6 

6.93 

— 

1030-1021 

68.5 

17.12 

29.9 

7.42 

115.0 

8.53 

8.01 

240-231 

1680.5 

103 

16.30 

651.7 

6.33 

112.8 

7.14 

1040-1031 

66.0 

16.50 

28.7 

7.17 

115.0 

8.25 

8.15 

250-241 

1768.0 

97 

18.22 

681.8 

7.02 

113.0 

7.94 

7.78 

1050-1041 

62.5 

15.62 

26.7 

6.67 

115.0 

7.67 

8.13 

260-251 

1681.0 

89 

18.90 

651.9 

7.31 

113.2 

8.27 

8.17 

1060-1051 

69.5 

17.37 

29.6 

7.37 

115.0 

8.47 

7.89 

270-261 

1575.5 

84 

18.76 

614.5 

7.31 

113.4 

8.29 

8.45 

1070-1061 

62.5 

4 

15.62 

26.2 

6.55 

115.0 

7.53 

7.77 

280-271 

1356.0 

71 

19.10 

649.0 

7.73 

113.6 

8.78 

8.66 

1080-1071 

44.5 

3 

14.85 

19.1 

6.36 

114.0 

7.31 

7.45 

290-281 

1299.5 

68 

19.10 

531.8 

7.82 

113.8 

8.90 

8.75 

1090-1081 

46.0 

15.33 

19.6 

6.53 

113.0 

7.50 

8.55 

300-291 

1144.0 

64 

17.88 

481.4 

7.52 

114.0 

8.57 

8.58 

1100-1091 

71.0 

23.67 

29.1 

9.70 

112.0 

10.85 

9.74 

310-301 

1117.5 

64 

17.45 

464.5 

7.25 

114.2 

8.28 

8.32 

1110-1101 

71.0 

3 

23.67 

28.9 

9.63 

111.0 

10.68 

9.71 

320-311 

1086.5 

63 

17.23 

446.9 

7.09 

114.4 

8.10 

8.21 

1120-1111 

33.0 

2 

16.50 

13.8 

6.90 

110.0 

7.60 

9.88 

330-321 

1111.0 

63 

17.61 

453.3 

7.20 

114.6 

8.25 

8.34 

1130-1121 

50.0 

25.00 

20.8 

10.40 

109.0 

11.35 

9.86 

.340-331 

1086.0 

59 

18.40 

446.0 

7.56 

114.8 

8.68 

8.45 

1140-1131 

48.0 

24.00 

19.7 

9.85 

108.0 

10.62 

11.29 

3.50-341 

1064.5 

59 

17.89 

431.7 

7.32 

115.0 

8.41 

8.63 

1150-1141 

64.0 

27.25 

22.2 

11.10 

107.0 

11.90 

12.71 

360-351 

1084.0 

57 

10.02 

436.4 

7.66 

115.0 

8.81 

8.67 

1160-1151 

73.0 

36..50 

29.5 

14.75 

106.0 

16.62 

12.85 

370-361 

1110.0 

67 

19.4.8 

436.3 

7.65 

115.0 

8.80 

9.02 

1170-1161 

60.5 

25.25 

20.1 

10.50 

105.0 

11.03 

13.03 

380-371 

1077.0 

52 

20.66 

428.9 

8.24 

115.0 

9.46 

9.06 

1180-1171 

60.6 

30.25 

23.9 

11.95 

104.0 

12.45 

11.83 

390-381 

1008.5 

52 

19.38 

403.0 

7.75 

115.0 

8.91 

9.23 

1190-1181 

59.5 

24.75 

23.3 

11.65 

103.0 

12.00 

12.57 

400-391 

1084.5 

52 

20.82 

422.2 

8.11 

115.0 

9.33 

9.23 

1200-1191 

67.0 

. 

33.50 

26.0 

13.00 

102.0 

13.26 

10.47 

410-401 

1075.0 

61 

21.08 

419.5 

8.22 

115.0 

9.45 

9.22 

1210-1201 

32.0 

16.00 

12.2 

6.10 

101.0 

6.16 

7.01 

120-411 

908.5 

47 

19.32 

363.9 

7.73 

115.0 

8.89 

9.12 

1220-1211 

8.5 

4.25 

3.2 

1.60 

100.0 

1.60 

3.09 

430-421 

840.0 

43 

19.53 

337.1 

7.85 

115.0 

9.03 

8.82 

1230-1221 

8.0 

4.00 

3.0 

1.50 

100.0 

1.60 

1.80 

440-431 

766.5 

41 

18.70 

309.2 

7.53 

115.0 

8.65 

8.78 

1240-1231 

12.6 

6.25 

4.6 

2.30 

100.0 

2.30 

1.93 

450-441 

768.0 

41 

18.75 

309.1 

7.53 

115.0 

8.65 

8.44 

1250-1241 

11.0 

5.50 

4.0 

2.00 

100.0 

2.00 

2.42 

460-451 

718.5 

40 

17.98 

278.8 

6.97 

115.0 

8.01 

7.95 

1260-1251 

16.5 

8.25 

5.9 

2.95 

100.0 

2.95 

2.73 

470-461 

546.5 

36 

15.18 

226.3 

6.25 

115.0 

7.19 

7.60 

1270-1261 

18.5 

9.25 

6.6 

3.25 

100.0 

3.25 

3.28 

480-471 

472.0 

30 

16.72 

200.1 

6.70 

115.0 

7.70 

7.39 

1280-1271 

21.5 

10.75 

7.3 

3.65 

100.0 

3.65 

3.65 

490-481 

348.5 

26 

13.40 

164.7 

6.32 

115.0 

7.27 

7.52 

1290-1281 

24.5 

12.25 

8.1 

4.05 

100.0 

4.05 

4.27 

500—401 

383.5 

26 

14.74 

171.9 

6.60 

115.0 

7.58 

7.37 

1300-1291 

32.0 

...... 

16.00 

10.4 

6.20 

100.0 

6.20 

6.27 

510-601 

33U.5 

24 

13.78 

151.2 

6.30 

115.0 

7.25 

1  7.24 

1310-1301 

42.0 

2 

21.00 

13.1 

6.65 

100.0 

6.56 

. 

*  At  240  B.  c.  the  number  of  i  easuremente  falls  below  100.  Previous  to  this  date,  in  order  to  avoid  violent  and  sudden  fluctuations  due  to  the  small  num* 
ber  of  trees,  the  mean  of  3  decades  has  been  substituted  for  the  values  of  column  H  In  our  final  curve  of  climatic  fluctuations,  fig.  50. 


Table  H. — Summary  of  Growth  of  Trees,  measured  hy  the  United  States  Forest  Service.  325 

When  the  number  of  trees  is  not  indicated,  it  is  the  same  as  the  figure  next  above  or  below  the  blank.  In  the  column  showing  average 
growth  the  figmes  under  A  indicate  the  values  where  allowance  is  made  for  the  dropping  out  of  group  after  group  of  trees  in  the 
earlier  centuries,  while  under  B  no  allowance  has  been  made.  Where  only  one  set  of  figures  is  given  in  the  column  of  average  growth, 
the  values  A  and  B  are  the  same.  In  plotting  the  curves  of  figure  31  the  values  under  B  have  in  all  cases  been  used.  (See  figure  31.) 


Date. 

Sequoia  Bempervirena. 

No.  of 
trees. 

Average 

A. 

growth. 

B. 

30 -year 
mean  of 
A. 

1901-1910 

— 

— 

— 

— 

1891-1900 

227 

0.352 

— 

1881-1890 

0.367 

— 

0.376 

1871-1880 

0.407 

— 

0.399 

1861-1870 

0.424 

— 

0.425 

1861-1860 

0.445 

— 

0.457 

1841-1860 

0.602 

— 

0.472 

1831-1840 

0.469 

_ 

0.479 

1821-1830 

0.467 

■  - 

0.486 

1811-1820 

0.620 

0.502 

1801-1810 

0.520 

— 

0.531 

1791-1800 

0.664 

_ 

0.529 

1781-1790 

0.612 

— 

0.524 

1771-1780 

0.606 

— 

0.514 

1761-1770 

0.624 

— 

0.630 

1761-1760 

0.561 

— 

0.557 

1741-1760 

0.586 

— 

0.580 

1731-1740 

0.692 

— 

0.589 

1721-1730 

0.588 

— 

0.591 

1711-1720 

0.592 

— 

0.684 

1701-1710 

227 

0.573 

— 

0.587 

1691-1700 

216 

0.596 

0.578 

1681-1690 

0.566 

— 

0.568 

1671-1680 

0.642 

— 

0.647 

1661-1670 

0.632 

— 

0.640 

1661-1660 

0.535 

— 

0.537 

1641-1650 

216 

0.543 

— 

0.538 

1631-1640 

208 

0.536 

— 

0.532 

1621-1630 

0.517 

— 

0.520 

1611-1620 

0.606 

— 

0.616 

1601-1610 

208 

0.625 

— 

0.525 

1591-1600 

201 

0.544 

_ 

0.638 

1581-1590 

0.545 

— 

0.541 

1671-1580 

0.534 

— 

0.537 

1561-1670 

0.633 

— 

0.532 

1561-1560 

0.629 

— 

0.531 

1541-1660 

ioi 

0.530 

— 

0.629 

1531-1540 

182 

0.529 

— 

0.536 

1621-1630 

0.549 

— 

0.638 

1511-1620 

182 

0.537 

— 

0.543 

1501-1510 

146 

0.642 

— 

0.560 

1491-1500 

0.672 

— 

0.562 

1481-1490 

0.571 

— 

0.572 

1471-1480 

0.573 

— 

0.574 

1461-1470 

0.677 

— 

0.584 

1461-1460 

146 

0.602 

— 

0.604 

1441-1460 

112 

0.633 

— 

0.619 

1431-1440 

0.622 

— 

0.626 

1421-1430 

0.624 

— 

0.617 

1411-1420 

0.606 

— 

0.602 

1401-1410 

112 

0.576 

— 

0.687 

1391-1400 

99 

0.578 

_ 

0.672 

1381-1390 

0.563 

— 

0.572 

1371-1380 

0.580 

— 

0.683 

1361-1370 

99 

0.606 

— 

0.676 

1351-1360 

83 

0.547 

— 

0.583 

1341-1350 

0.696 

— 

0.582 

1331-1340 

0.602 

— 

0.598 

1321-1330 

83 

0..596 

— 

Red  Fir,  Tahoe,  California. 

Red  Fir,  Idaho. 

Dougins  Fir,  Idaho. 

No.  of 
trees. 

Average  growth 

30-year 
mean  of 
A. 

No.  of 
trees. 

Average  growth. 

30-year 
mean  of 
A. 

No.  of 
trees. 

Average  growth. 

30-year 
mean  of 
A. 

A. 

B. 

A. 

B. 

A. 

B. 

68 

0.501 

0.462 

0.460 

0.443 

0.472 

0.462 

0.446 

0.463 

0.492 

0.543 

0.481 

0.488 

0.459 

0.487 

0.498 

0.512 

0.551 

0..545 

0.565 

0.524 

0.540 

0.509 

0.544 

0.547 

0.510 

0.501 

0.438 

0.397 

0.421 

0.470 

0.637 

0.652 

0.592 

0.633 

0.663 

0.655 

0.620 

— 

0.474 

0.455 

0.458 

0.462 

0.460 

0.457 

0.467 

0.499 

0.505 

0.504 

0.476 

0.478 

0.481 

0.499 

0.520 

0.536 

0.554 

0.646 

0.543 

0.524 

0.631 

0.533 

0.534 

0.519 

0.483 

0.445 

0.419 

0.429 

0.476 

0.653 

0.594 

0.624 

0.629 

0.650 

(0.613) 

73 

0.402 

0.431 

0.431 

0.439 

0.439 

0.488 

0.508 

0.570 

0.685 

0.450 

0.438 

0.570 

0.614 

0.568 

0.475 

0.557 

0.585 

0.538 

0.632 

0.591 

0.537 

0.517 

0.645 

0.690 

0.750 

— 

0.421 

0.434 

0.436 

0.455 

0.478 

0.522 

0.554 

0.635 

0.491 

0.486 

0.507 

0.551 

0.519 

0.633 

0.539 

0.560 

0.585 

0.587 

0.587 

0.548 

0.566 

0.617 

(0.695) 

29 

0.300 

0.400 

0.417 

0.345 

0.414 

0.370 

0.284 

0.402 

0.445 

0.467 

0.335 

0.310 

0.370 

0.394 

0..391 

0.416 

0.455 

0.381 

0.371 

0.399 

0.461 

0.405 

0.478 

0.430 

— 

0.372 

0.387 

0.392 

0.376 

0.356 

0.352 

0.377 

0.435 

0.412 

0.367 

0.338 

0.358 

0.385 

0.400 

0.421 

0.414 

0.402 

0.384 

0.410 

0.422 

0.448 

(0.438) 

68 

42 

73 

61 

46 

34 

29 

(18 

29 

28 

26 

22 

(14 

0.642 

0.657 

0.603 

0.622 

0.686 

0.473 

0.400 

0.360 

0.377 

0.430 

0.377 

0.544 

0.473 

0.507 

0.532 

0.624 

0.482) 

0.540 

0.497 

0.498 

0.533 

0.608) 

0.450 

0.402 

0.469 

0.418) 

42 

32 

32 

22 

22 

(12 

' 

326  Table  H. — Summary  of  Growth  of  Trees,  measured  by  United  States  Forest  Service — Continued. 


Jeffrey  Pine,  S.  California. 

Sugar  Pine,  S.  Calif. 

Bull  Pina,  S.  Calif. 

Shortleaf  Pine,  Arkansas. 

Date. 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  growth. 

30-3rear 

No.  of 

Average 

1 

1 

30-yesr 

No.  of 

Average  growth. 

30-year 

trees. 

A. 

B. 

A. 

trees. 

A. 

B. 

A. 

trees. 

A. 

B. 

A. 

trees. 

A. 

B. 

A. 

iQni-isio 

177 

O.fiOS 

iftQi-idon 

0.722 

0.620 

31 

0.71 

32 

0.584 

245 

0.393 

IKftl-IHOO 

0.630 

0.658 

0.81 

0.77 

0.610 

0.612 

0.353 

0.382 

1871-1880 

0.621 

0.603 

0.78 

0.82 

0.641 

0.622 

0.401 

0.369 

1861-1870 

0.558 

_ 

0.587 

0.86 

0.81 

0.615 

0.614 

0.352 

0.384 

1851-1860 

0.581 

0.557 

0.79 

0.83 

0.585 

0.595 

0.399 

0.382 

1841-1850 

0.532 

0.663 

0.83 

0.85 

0.585 

0.586 

0.394 

0.372 

1831-1840 

0.577 

0.568 

0.94 

0.85 

0.588 

0.599 

0.323 

0.349 

1821-1830 

0.564 

0.571 

0.77 

0.86 

0.625 

0.609 

0.331 

0.361 

1811-1820 

0.572 

0.602 

0.88 

0.86 

0.613 

0.603 

0.428 

0.388 

1801-1810 

0.661 

0.630 

0.94 

0.86 

0.570 

0.584 

0.405 

0.407 

1791-1800 

0.657 

0.644 

0.77 

0.83 

0.570 

0.571 

0.388 

0.399 

1781-1790 

0.614 

0.631 

0.78 

0.81 

0.573 

0.579 

0.403 

0.406 

1771-1780 

0.623 

0.612 

0.87 

0.83 

0.594 

0.573 

0.427 

0.413 

1761-1770 

0.600 

0.610 

0.83 

0.80 

0.651 

0.564 

0.409 

0.421 

1751-1760 

0.606 

0.631 

0.70 

0.77 

0.546 

0.544 

0.428 

0.431 

1741-1760 

0.687 

0.648 

0.78 

0.75 

0.535 

0.539 

0.456 

0.428 

1731-1740 

0.652 

0.667 

0.77 

0.78 

0.536 

0.560 

0.399 

0.406 

1721-1730 

0.663 

0.633 

0.79 

0.80 

0.611 

- 

0.574 

0.363 

0.379 

1711-1720 

177 

0.584 

0.630 

0.85 

0.85 

0.576 

0.586 

0.376 

0.372 

1701-1710 

68 

0.643 

0.651 

0.618 

0.90 

0.88 

0.570 

0.568 

245 

0.377 

0.372 

1691-1700 

0.627 

0.668 

0.630 

0.87 

0.90 

32 

0.558 

0.560 

170 

0.363 

0.366 

0.370 

1681-1690 

0.621 

0.659 

0.600 

0.94 

0.94 

21 

0.551 

0  5.53 

0.546 

95 

0  369 

0..391 

0.348 

1671-1680 

0.553 

0.606 

0.572 

1.00 

0.95 

0.528 

0,530 

0.549 

31 

0.313 

0.366 

(0.324) 

1661-1670 

68 

0.541 

0.595 

0.569 

0.92 

0.96 

0.569 

0.571 

0.542 

(16 

0.289 

0.316) 

1651-1660 

26 

0.603 

0.632 

0.585 

0.97 

0.95 

21 

0.528 

0.530 

(0.546) 

1641-1650 

0.612 

0.626 

0.612 

0.97 

0.92 

(U 

0.541 

0.635) 

1631-1640 

0.620 

0.636 

0.613 

0.81 

0.87 

1621-1630 

0.608 

0.609 

0.620 

31 

0.84 

1611-1620 

26 

0.633 

0.685 

(0.627) 

1601-1610 

(10 

0.640 

0.688) 

1591-1600 

1581-1590 

1571-1580 

1561-1570 

1551-1560 

1541-1550 

1531-1540 

1521-1530 

1511-1520 

1501-1610 

White  Oak,  Missouri. 

White  Oak, 

West  Virginia. 

Tulip  Poplar,  West  Virginia. 

Beech,  Lewis  Co.,  New  York. 

Date. 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  gro^^. 

30-year 

trees. 

A. 

B. 

A. 

trees. 

A. 

B. 

mean  of 
A. 

trees. 

A. 

B. 

mean  of 
A. 

trees. 

A. 

B. 

mean  of 
A. 

1901-1910 

-  -  - 

, 

_ 

1891-1900 

26 

0.621 

728 

0.63 

107 

0.334 

46 

0  505 

1881-1890 

0.674 

0.633 

0.68 

0.65 

0.365 

0  .3.52 

0  .577 

0576 

1871-1880 

0.604 

0.637 

0.63 

0.66 

.  0.358 

0  .345 

0647 

0  .583 

1861-1870 

0.632 

0.620 

0.66 

0.62 

0.313 

0  331 

0525 

0  .558 

1851-1860 

0.625 

0.645 

0.58 

0.61 

0  322 

0  332 

0  502 

0.514 

1841-1850 

0.678 

0.670 

0.60 

0.58 

0  331 

0331 

051 5 

0  515 

1831-1840 

0.706 

0.677 

0.56 

0.58 

0341 

n,.3.32 

0  529 

0.534 

1821-1830 

0.648 

0.635 

0.59 

0.58 

0  323 

9329 

05.58 

0  559 

1811-1820 

0.551 

0.602 

0.59 

0.60 

0  324 

0331 

0589 

0  .577 

1801-1810 

0.606 

0.604 

0.61 

0.62 

0.349 

n  340 

0  583 

0.577 

1791-1800 

0.653 

0.653 

0.67 

0.66 

0  348 

0  3.50 

0  559 

0..548 

1781-1890 

0.698 

0.703 

0.71 

0.70 

0  352 

0  .34.3 

0  503 

0.513 

1771-1780 

0.756 

0.693 

0.71 

0.68 

0.3.30 

0  3.36 

0  478 

0.493 

1761-1770 

0.625 

0.665 

0.62 

0.63 

0.327 

0  327 

0  499 

0.486 

1751-1760 

0.613 

0.637 

0.55 

0  58 

0  .324 

0  .326 

0  481 

0  485 

1741-1750 

0.673 

0.675 

0.56 

0.57 

0  327 

0  330 

0  475 

0  486 

1731-1740 

0.740 

0.750 

0.59 

0.58 

0  3.30 

0  337 

0.501 

0  496 

1721-1730 

0.837 

0.788 

0.59 

0.60 

n..344 

0  340 

0.512 

0.523 

1711-1720 

0.788 

0.796 

0.63 

0.611 

0  338 

0  344 

0.557 

0  535 

1701-1710 

26 

0.762 

0.754 

728 

0.613 

0.621 

107 

0  .349 

0  .349 

46 

0.536 

0  529 

1691-1700 

25 

0.713 

0.691 

0.694 

620 

0.620 

0.64 

0.629 

91 

0.361 

0.355 

0.347 

36 

0.484 

0.478 

0.513 

1681-1690 

25 

0.607 

0.575 

0.657 

446 

0.593 

0.62 

0.608 

76 

0.332 

0.320 

0.347 

26 

0.520 

0.511 

0.491 

1671-1680 

23 

0.652 

0.560 

(0.628) 

252 

0.612 

0.63 

0.605 

62 

0.347 

0.343 

0.342 

20 

0.469 

0.491 

(0.493) 

1661-1670 

(17 

0.625 

0.553) 

13t 

0.611 

0.62 

0.613 

51 

0.346 

0  3.36 

0  .342 

(13 

0.485 

0.417) 

1651-1660 

82 

0  615 

0.63 

0  618 

38 

0  3.32 

0  314 

0  335 

1641-1650 

60 

0.629 

0  53 

0  6.30 

30 

0  328 

n..3n.5 

0  350 

1631-1640 

54 

0.647 

0.58 

0  6.51 

21 

0389 

03.50 

(0.379) 

1621-1630 

44 

0.676 

C.58 

0  680 

(13 

0.420 

0.345) 

1611-1620 

31 

0.707 

0.54 

(0.720) 

1601-1610 

(18 

0.778 

0.56) 

Table  H. — Summary  of  Growth  of  Trees,  measured  by  United  States  Forest  Service — Continued 


327 


Date. 


1901-1910 

1891-1900 

1881-1890 

1871-1880 

1861-1870 

1851-1860 

1841-1850 

1831-1840 

1821-1830 

1811-1820 

1801-1810 

1791-1800 

1781-1790 

1771-1780 

1761-1770 

1751-1760 

1741-1750 

1731-1740 

1721-1730 

1711-1720 

1701-1710 

1691-1700 

1681-1690 

1671-1680 

1661-1670 

1651-1660 

1641-1650 

1631-1640 

1621-1630 

1611-1620 

1601-1610 

1591-1600 

1581-1590 

1571-1580 

1561-1570 

1551-1560 

1541-1550 

1531-1540 

1521-1530 

1511-1520 

1501-1510 

1491-1500 


Yellow  Pine,  Idaho. 

Yellow  Pine,  New  Mexico. 

Spruce,  West  Virginia. 

Red  Spruce,  Maine. 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  growth. 

30-year 

No.  of 

Average  growth. 

30-year 

trees. 

A. 

B. 

mean  of 
A. 

trees. 

A. 

B. 

mean  of 
A. 

trees. 

A. 

B. 

A. 

trees. 

A. 

B. 

A. 

217 

0.204 

272 

0.260 

0.205 

0.202 

0.236 

0.238 

223 

0.380 

• 

163 

0.255 

0.198 

0.203 

0.217 

0.227 

0.287 

0.327 

0.235 

0.229 

0.207 

0.196 

0.227 

0.226 

0.313 

0.327 

0.197 

0.217 

0.182 

0.190 

0.234 

0.234 

0.380 

0.337 

0.218 

0.224 

0.182 

0.177 

0.241 

0.239 

0.317 

0.340 

0.257 

0.243 

0.166 

0.191 

0.243 

0.240 

0.324 

0.321 

0.265 

0.263 

0.206 

0.196 

0.235 

0.234 

0.322 

0.322 

0.267 

0.270 

0.215 

0.206 

0.223 

0.231 

0.320 

0.322 

0.277 

0.257 

0.204 

0.201 

0.236 

0.236 

0.324 

0.317 

0.226 

0.241 

0.184 

0.181 

0.250 

0.247 

0.310 

0.300 

0.181 

0.192 

0.154 

0.16S 

0.255 

0.251 

0.269 

0.278 

0.170 

0.181 

0.166 

0.168 

0.250 

0.251 

0.254 

0.277 

0.193 

0.182 

0.185 

0.172 

0.250 

0.251 

0.309 

0.294 

0.183 

0.186 

0.164 

0.172 

0.253 

0.250 

0.319 

0.311 

0.183 

0.193 

0.167 

0.168 

0.248 

0.250 

0.304 

0.307 

0.213 

0.198 

0.173 

0.172 

0.250 

0.251 

0.299 

0.298 

0.198 

0.200 

0.177 

0.173 

0.254 

0.252 

0.290 

0.293 

0.190 

0.195 

0.169 

0.170 

0.252 

0.253 

0.291 

0.290 

0.196 

0.196 

217 

0.164 

0.168 

0.254 

0.252 

0.306 

0.300 

0.201 

0.215 

213 

0.172 

0.174 

0.169 

272 

0.251 

0.251 

223 

0.302 

0.306 

163 

0.249 

0.238 

205 

0.171 

0.174 

0.170 

246 

0.247 

0  246 

0.248 

204 

0.309 

0.305 

0.327 

151 

0.265 

0.269 

0.268 

187 

0.168 

0.173 

0.168 

208 

0.246 

0.245 

0.249 

179 

0.340 

0.334 

0.326 

142 

0.290 

0.303 

0.279 

169 

0.164 

0.172 

0.159 

178 

0.255 

0.252 

0.259 

147 

0.328 

0.305 

0.330 

129 

0.281 

0.294 

0.265 

156 

0.144 

0.155 

0.151 

149 

0.276 

0.268 

0.272 

126 

0.321 

0.283 

0.319 

110 

0.223 

0.239 

0.228 

150 

0.144 

0.154 

0.147 

113 

0.286 

0.277 

0.289 

102 

0.308 

0.235 

0.318 

93 

0.180 

0.185 

0.203 

136 

0.153 

0.162 

0.145 

87 

0.295 

0.281 

0.289 

85 

0.324 

0.228 

0.331 

73 

0.206 

0.213 

0.189 

106 

0.137 

0.145 

0.154 

67 

0.285 

0.276 

0.282 

66 

0.368 

0.238 

0.370 

58 

0.182 

0.162 

0.195 

67 

0.171 

0.199 

0.155 

50 

0.267 

0.267 

0.272 

60 

0.417 

0.273 

0..398 

47 

0.196 

0.159 

0.188 

56 

0.156 

0.185 

0.158 

34 

0.266 

0.275 

0.272 

45 

0.410 

0.255 

0.417 

38 

0.185 

0.149 

0.202 

51 

0.147 

0.183 

0.147 

(18 

0.285 

— ) 

37 

0.423 

0.274 

0.433 

33 

0.226 

0.167 

0.219 

49 

0.137 

0.176 

0.142 

27 

0.465 

0.308 

(0.467) 

26 

0.245 

0.171 

0.260 

48 

0.141 

0.182 

0.140 

(19 

0.513 

0.308) 

20 

0.310 

0.216 

(0.302) 

44 

0.143 

0.182 

0.137 

(16 

0.352 

0.241) 

43 

0.127 

0.166 

0.127 

41 

0.112 

0.152 

0.119 

38 

0.118 

0.160 

0.105 

38 

0.085 

0.127 

0.097 

34 

0.089 

0.131 

0.093 

29 

0.105 

0.148 

0.098 

25 

0.101 

0.145 

0.108 

22 

0.118 

0.161 

328  Table  I. — Average  Annual  Growth  of  Sequoias. 

Groups  I  to  III  are  mature  trees  at  Hume.  Sections  were  cut  from  them  in  1912.  Groups  marked  A  grew  in  damp  places;  those 
marked  B  in  dry  places.  The  trees  of  Group  IV  consist  of  young  trees  that  grew  at  Dillonwood;  those  in  group  “A”  are  trees 
which  began  to  grow  before  1800  a.  d.  ;  those  in  group  B  are  trees  which  began  to  grow  before  1883.  Group  V  consists  of 
mature  trees  which  were  cut  in  1911  at  Camp  No.  2,  Hume.  The  number  of  trees  and  measurements  is  as  follows:  I — A,  22  trees, 
23  measurements;  I — B,  14  trees,  14  measurements;  II — A,  25  trees,  31  measurements;  II — B,  18  trees,  18  measurements;  III — A, 
22  trees,  25  measurements;  IV — a,  5  trees,  8  measurements;  IV — b,  19  trees,  46  measurements;  V — A,  11  trees,  18  measurements. 
(See  figures  42,  43,  44,  and  48.) 


Date. 

Group  I. 

Grou 

pll. 

Group  III. 

Group  IV. 

Group  V. 

Mean  of  Groups  I-III. 

Differential 
growth  derived 
from  weighted 
means. 

Mean  growth 
of  groups 

I,  II,  III,  V. 
Weighted.* 

A. 

B. 

A 

B. 

A. 

a. 

h. 

A. 

Weighted. 

Un¬ 

weighted.* 

1910 

2.92 

3.14 

1.64 

1.72 

1.21 

1.45 

4.05 

1.41 

3.29 

2.01 

-0.29 

2.82 

1909 

2.95 

3.38 

1.91 

1.88 

1.28 

1.30 

4.05 

1.37 

3.58 

2.16 

-0.80 

3.03 

1908 

3.09 

3.81 

1.74 

2.03 

1.34 

1.31 

4.12 

1.38 

3.66 

224 

+0.44 

3.09 

1907 

2,70 

3.20 

1.51 

1.84 

1.17 

1.51 

3.95 

1.39 

3.22 

1.95 

+0.22 

2.76 

1906 

2.56 

2.79 

1.42 

1.54 

1.21 

1.45 

3.20 

1.38 

300 

1.80 

-0.27 

2.60 

1905 

2.91 

3.36 

1.48 

1.88 

1.18 

1.38 

3.05 

1.35 

3.27 

2.05 

-0.36 

2.79 

1904 

2.94 

3.70 

1.60 

1.79 

1.20 

1.35 

3.73 

1.18 

3.63 

2.08 

+0.43 

3.02 

1903 

2.83 

3.50 

1.44 

1.70 

1.19 

1.68 

4.63 

1.41 

3.20 

1.96 

-0.20 

2.75 

1902 

3.20 

3.76 

1.43 

1.92 

1.23 

1.40 

4.08 

1.40 

3.40 

2.12 

+0.12 

2.90 

1901 

3.40 

3.53 

1.35 

1.83 

1.17 

1.38 

4.59 

1.30 

3.28 

2.07 

+0.29 

2.79 

1900 

3.03 

3.25 

1.28 

1.63 

1.05 

1.41 

4.72 

1.23 

2.99 

1.89 

-0.07 

2.65 

1899 

2.94 

3.31 

1.23 

1.73 

1.16 

1.39 

4.34 

1.26 

3.06 

1.91 

-0.50 

2.61 

1898 

3.38 

3.93 

1.57 

1.98 

1.25 

1.29 

4.32 

1.22 

3.56 

2.24 

-0.40 

2.93 

1897 

4.58 

4.51 

1.76 

1.90 

1.28 

1.36 

4.64 

1.44 

3.96 

2.60 

-0.34 

3.33 

1896 

4.63 

4.78 

2.00 

1.93 

1.47 

1.35 

3.90 

1.68 

4.30 

2.76 

*0.00 

3.60 

1895 

4.37 

4.93 

2.00 

1.87 

1.54 

1.53 

4.23 

1.55 

4.30 

2.74 

+0.49 

3.61 

1894 

3.82 

4.31 

1.76 

2.05 

1.22 

1.65 

4.35 

1.62 

3.81 

2.44 

+0.45 

3.26 

1893 

3.67 

3.63 

1.63 

1.54 

1.06 

1.30 

4.44 

1.48 

3.36 

2.17 

-0.07 

2.88 

1892 

3.52 

3.71 

1.54 

1.74 

1.14 

1.39 

4.32 

1.35 

3.43 

2.20 

-0.08 

2.91 

1891 

3.52 

4.23 

1.50 

1.98 

1.12 

1.05 

4.35 

1.34 

3.51 

2.25 

+0.25 

2.97 

1890 

3.56 

3.43 

1.47 

1.72 

1.06 

1.26 

4.46 

1.48 

3.26 

2.10 

-0.23 

2.82 

1889 

3.54 

4.40 

1.62 

1.80 

1.19 

1.29 

3.60 

1.23 

3.59 

2.30 

+0.16 

3.00 

1888 

3.47 

4.06 

1.58 

1.68 

1.14 

1.41 

3.98 

1.34 

3.43 

2.18 

-0.29 

2.91 

1887 

4.07 

4.20 

1.72 

1.79 

1.20 

1.30 

3.73 

1.20 

3.72 

2.35 

-0.65 

3.09 

1886 

4.57 

5.35 

2.01 

2.26 

1.30 

1.36 

3.52 

1.24 

4.37 

2.72 

+0.41 

3.64 

1885 

4.32 

5.05 

1.68 

2.09 

1.17 

1.58 

3.70 

1.33 

3.96 

2.43 

+0.31 

3.30 

1884 

4.11 

4.08 

1.63 

1.82 

1.15 

1.19 

3.64 

1.28 

3.65 

2.18 

+0.27 

3.05 

1883 

3.58 

4.01 

1.56 

1.88 

1.16 

1.35 

3.59 

1.15 

3.38 

2.14 

-0,32 

3.81 

1882 

3.64 

4.23 

1.72 

2.21 

1.17 

1.34 

3.75 

1.32 

3.70 

2.27 

+0.64 

3.11 

1881 

3.36 

3.35 

1.41 

1.82 

0.98 

1.65 

3.87 

1.51 

3.06 

1.74 

-0.06 

2.72 

1880 

2.66 

3.41 

1.44 

1.82 

1.02 

1.11 

3.42 

1.26 

3.12 

1.80 

+0.04 

2.62 

1879 

2.85 

3.86 

1.37 

1.99 

0.95 

(1.53) 

1.42 

3.08 

1.87 

+0.14 

2.69 

1878 

2.73 

3.02 

1.36 

1.77 

0.93 

(1.38) 

1.52 

2.94 

1.72 

-0.18 

2.63 

1877 

2.53 

3.36 

1.43 

1.78 

1.02 

1  51 

8.12 

1  77 

—0.74 

2,74 

1876 

2.76 

3.22 

1.84 

2.33 

1.18 

1.42 

.^.86 

2.04 

44).60 

8  26 

1875 

2.55 

2.93 

1.54 

1.85 

1.06 

1.68 

3  26 

1.77 

—080 

2.87 

1874 

2.60 

3.15 

1.80 

1.97 

1.06 

1.56 

.8.66 

1.91 

4-0.80 

3.07 

1873 

2.35 

2.82 

1.55 

1.79 

1.08 

1.61 

3.26 

1.60 

4-0  10 

2.88 

1872 

2.44 

3.16 

1.63 

1.59 

1.00 

1.43 

8.16 

1.70 

—0  .88 

2  74 

1871 

2.52 

3.32 

1.75 

1.83 

1.12 

1 

8.49 

1  86 

—0  46 

3,02 

1870 

3.07 

3.40 

2.06 

2.07 

1.22 

1.62 

8  97 

2.12 

4-0  1.6 

3,36 

1869 

3.07 

4.28 

1.80 

2.27 

1.20 

1.64 

3.82 

2.12 

4*0  26 

3.29 

1868 

3.68 

4.37 

1.76 

1.96 

1.12 

1.64 

3.57 

2.03 

4-0  41 

3  08 

1867 

2.71 

3.39 

1.58 

1.75 

0.97 

1.58 

3.16 

1.75 

—Oil 

2.80 

1866 

2.95 

3.11 

1.67 

1.82 

0.98 

1,61 

3.27 

1,79 

4-0  09 

2.90 

1865 

2.36 

3.24 

1.56 

1.89 

0.94 

1.67 

3.18 

1  66 

—036 

2.86 

1864 

1.91 

1.99 

0.90 

1  72 

g  64 

1  37 

4_0  10 

1863 

1.68 

1.90 

1  04 

1,55 

3  gg 

1  87 

1862 

1.81 

1.88 

1.07 

1,72 

3  61 

1  86 

1861 

1.64 

1.73 

0.90 

1  g1 

3  20 

1  60 

1860 

1.49 

1.55 

0.93 

1  67 

1859 

1.49 

1.74 

0  90 

1  7g 

3  ftl 

1858 

1.75 

2.01 

0  88 

1  8? 

1857 

1.68 

1.94 

0  87 

?  00 

1856 

1.84 

2.04 

0.85 

2  11 

1855 

1.91 

2.04 

0  90 

1  71 

1854 

1.94 

2.28 

0.88 

1853 

2.07 

2.12 

0.89 

-0.03 

1852 

1.97 

1  95 

0  Q4 

1851 

2.07 

2.03 

1  06 

1  70 

3  79 

1850 

2.11 

2.09 

1  06 

1  76 

O.Ar«7 

1849 

1.98 

2.03 

0.99 

2,07 

1  67 

1848 

1.89 

1.88 

0.98 

1  61 

3  29 

1.58 

+0.04 

1847 

1.63 

1.74 

0.88 

1  81 

2  9.6 

7  QQ 

1846 

1.65 

1.67 

0.94 

1  62 

8.16 

?  Q4 

1845 

1.38 

1.71 

0.92 

158 

8  09 

1844 

1.36 

1.76 

0.93 

1.89 

8  12 

?  7? 

1843 

1.33 

1.79 

1.03 

i..5a 

3.46 

3  Oi 

1842 

1.70 

1.60 

1.04 

1.51 

8  49 

300 

1841 

1.73 

1.62 

1.12 

1.42 

3.76 

3.07 

means  are  obtained  by  adding  all  the  totals  and  dividing  by  the  number  of  measurements.  In  the  weighted  means  the  different  groups 
ave  Deen  given  aucn  a  weight  that  the  value  of  a  single  measurement  is  the  same,  no  matt>er  whether  the  average  growth  of  the  group  is  great  or  small* 


Table  I. — Average  Annual  Growth  of  ^egwoias— Continued 


329 


Date. 

Group  II. 

Group 

III. 

Group  V. 

Mean  of 
Groups 
I-III. 
Weighted. 

Mean  growth 
of  groups 

1,  2,  3,  5. 
Weight^.* 

Group  V. 

Group  V. 

Group  V. 

Group  V. 

A. 

B. 

A. 

A. 

Date. 

A. 

Date. 

A. 

Date. 

A. 

Date. 

A. 

1840 

1.80 

1.72 

1.20 

1.41 

4.03 

3.19 

1760 

1.51 

1680 

1.86 

1600 

1.40 

1520 

2.02 

1839 

1.68 

1.61 

1.22 

1.27 

4.09 

3.10 

1769 

1.39 

1679 

1.-83 

1599 

1.59 

1519 

2.08 

1838 

1.69 

1.67 

1.14 

1.49 

3.83 

3.16 

1758 

1.60 

1678 

1.85 

1598 

1.53 

1518 

1.91 

1837 

1.66 

1.68 

1.15 

1.66 

3.86 

3.22 

1757 

1.49 

1677 

1.87 

1597 

1.62 

1517 

1.94 

1836 

1.61 

1.65 

1.20 

1.40 

4.03 

3.25 

1756 

1.45 

1676 

1.89 

1596 

1.74 

1516 

2.25 

1836 

1.66 

2.06 

1.31 

1.68 

4.40 

3.52 

1765 

1.92 

1675 

1.88 

1595 

1.72 

1515 

1.94 

1834 

1.87 

2.44 

1.26 

1.41 

4.23 

3.29 

1764 

1.67 

1674 

1.82 

1594 

1.60 

1514 

1.65 

1833 

1.91 

2.24 

1.20 

1.40 

4.03 

3.18 

1753 

1.65 

1673 

1.73 

1593 

1.79 

1513 

1.67 

1832 

1.67 

2.36 

1.01 

1.68 

3.39 

3.01 

1762 

1.56 

1672 

1.76 

1592 

1.74 

1512 

1.71 

1831 

1.66 

1.67 

1.05 

1.67 

3..52 

3.14 

1761 

1.70 

1671 

1.43 

1591 

1.53 

1511 

1.83 

1830 

1.66 

1.67 

0.88 

1.42 

2.95 

2.65 

1750 

1.66 

1670 

1.67 

1590 

1.67 

1510 

2.16 

1829 

1.58 

1.76 

0.90 

1.37 

3.02 

2.64 

1749 

1.63 

1669 

1.83 

1589 

1.67 

1509 

1.98 

1828 

1.62 

1.73 

1.00 

1.65 

3.36 

3.05 

1748 

1.71 

1668 

1.90 

1588 

1.92 

1508 

1.98 

1827 

1.40 

0.88 

1.27 

•2.95 

•2.63 

1747 

1.62 

1667 

1.75 

1587 

1.75 

1607 

1.87 

1826 

1.53 

0.96 

1.50 

3.22 

2.86 

1746 

1.59 

1666 

1.73 

1586 

1.63 

1506 

2.27 

1826 

1.42 

0.89 

1.60 

2.98 

2.82 

1746 

1.57 

1665 

1.91 

1585 

1.67 

1505 

2.29 

1824 

1.52 

0.89 

1.61 

2.98 

2.74 

1744 

1.60 

1664 

1.82 

1584 

1.19 

1504 

2.37 

1823 

1.34 

0.94 

1.51 

3.16 

2.84 

1743 

1.61 

1663 

2.01 

1583 

1.52 

1822 

1.56 

1.06 

1.65 

3.66 

3.14 

1742 

1.64 

1662 

1.77 

1582 

1.49 

1821 

2.09 

C.90 

1.81 

3.02 

3.03 

1741 

1.43 

1661 

1.93 

1581 

1.59 

1820 

1.97 

0.89 

1.54 

2.98 

2.77 

1740 

1.49 

1660 

1.79 

1580 

1.54 

1819 

1.91 

0.94 

1.59 

3.18 

2.90 

1739 

1.54 

1659 

1.54 

1579 

1.48 

1818 

1.73 

0.97 

1.69 

3.26 

2.94 

1738 

1.72 

1658 

1.72 

1578 

1.59 

1817 

1.03 

1.56 

3.45 

3.02 

1737 

1.51 

1857 

1.58 

1577 

1.65 

1816 

1.19 

1.69 

3.99 

3.40 

1736 

1.32 

1656 

1.62 

1576 

1.59 

1815 

1.21 

1.67 

4.06 

3.33 

1735 

1.53 

1655 

1.57 

1575 

1.52 

1814 

1.29 

1.63 

4.33 

3.51 

1734 

1.81 

1654 

1.65 

1674 

1.75 

1813 

1.22 

1.63 

4.09 

3.26 

1733 

1.74 

1653 

1.67 

1573 

1.97 

1812 

1.38 

1.72 

4.63 

3.74 

1732 

1.84 

1652 

1.77 

1572 

2.06 

1811 

1.35 

1.81 

4.09 

3.59 

1731 

1.81 

1651 

1.81 

1571 

1.78 

1810 

1.24 

1.61 

3.57 

3.17 

1730 

1.53 

1650 

1.82 

1570 

1.86 

1809 

1.21 

1.80 

3.31 

3.29 

1729 

1.66 

1649 

1.66 

1569 

1.81 

1808 

1.76 

2.74 

3.02 

1728 

1.94 

1648 

1.87 

1568 

2.05 

1807 

1.74 

2.77 

3.01 

1727 

1.86 

1647 

1.68 

1567 

1.78 

1806 

1.63 

2.82 

2.91 

1726 

2.28 

1646 

1.74 

1566 

1.88 

1806 

1.78 

3.11 

3.18 

1725 

1.73 

1645 

1.68 

1565 

1.94 

1804 

1.80 

3.11 

3.22 

1724 

1.44 

1644 

1.88 

1564 

2.12 

1803 

1.91 

3.97 

3.87 

1723 

1.47 

1643 

1.90 

1563 

2.14 

1802 

1.95 

3.40 

3.49 

1722 

1.67 

1642 

1.70 

1562 

2.01 

1801 

1.85 

2.91 

3.20 

1721 

1.64 

1641 

2.02 

1561 

1.96 

1800 

1.86 

2.66 

3.11 

1720 

1.55 

1640 

1.87 

1560 

2.02 

1799 

1.60 

2.65 

2.81 

1719 

1.68 

1639 

1.90 

1559 

1.97 

1798 

1.67 

2.48 

2.82 

1718 

1.66 

1638 

1.72 

1558 

1.83 

1797 

1.68 

2.33 

2.78 

1717 

1.67 

1637 

1.65 

1557 

2.05 

1796 

1.53 

2.19 

2.66 

1716 

1.96 

1636 

1.72 

1556 

1.69 

1796 

1.50 

3.30 

2.94 

1716 

1.79 

1635 

1.90 

1555 

1.92 

1794 

1.5-1 

4.29 

3.36 

1714 

1.74 

1634 

1.94 

1554 

1.96 

1793 

1.71 

3.39 

3.22 

1713 

1.65 

1633 

1.92 

1653 

1.82 

1792 

1.88 

3.23 

3.36 

1712 

1.85 

1632 

1.89 

1552 

1.53 

1791 

1.78 

3.23 

3.23 

1711 

1.91 

1631 

1.80 

1551 

1.67 

1790 

1.94 

2.97 

3.32 

1710 

1.96 

1630 

1.84 

1550 

1.68 

1789 

1.82 

3.36 

2.96 

1709 

1.80 

1629 

1.23 

1549 

1.49 

1788 

1.90 

3.00 

3.29 

1708 

1.94 

1628 

2.04 

1548 

1.43 

1787 

1.77 

2.48 

2.94 

1707 

2.00 

1627 

1.98 

1547 

1.35 

1786 

1.66 

2.68 

2.90 

1706 

2.13 

1626 

1.87 

1546 

1.55 

1785 

1.69 

2.33 

2.79 

1705 

2.01 

1625 

1.98 

1645 

1.83 

1784 

1.67 

2.25 

2.74 

1704 

1.95 

1624 

2.08 

1544 

1.84 

1783 

1.47 

2.62 

2.66 

1703 

2.01 

1623 

2.09 

1543 

1.83 

1782 

1.41 

2.91 

2.70 

1702 

1.78 

1622 

2.16 

1542 

2.54 

1781 

1.38 

3.08 

2.73 

1701 

1.57 

1621 

2.29 

1541 

2.18 

1780 

1.70 

2.77 

2.97 

1700 

1.61 

1620 

2.38 

1540 

2.14 

1779 

1.47 

2.97 

2.78 

1699 

1.62 

1619 

2.66 

1539 

2.18 

1778 

1.29 

2.97 

2.68 

1698 

1.68 

1618 

2.30 

1533 

2.18 

1777 

1.47 

4.24 

3.26 

1697 

1.68 

1617 

2.49 

1537 

1.97 

1776 

1.53 

3.86 

3.18 

1696 

1.73 

1616 

2.47 

1636 

2.14 

1775 

1.56 

3.65 

3.11 

1695 

1.71 

1615 

2.62 

1536 

2.10 

1774 

1.55 

3.26 

2.99 

1694 

1.78 

1614 

2.60 

1534 

1.85 

1773 

1.41 

3.26 

2.82 

1693 

1.67 

1613 

2.52 

1533 

1.97 

1772 

1.43 

3.00 

2.75 

1692 

1.74 

1612 

2.68 

1532 

2.22 

1771 

1.46 

3.26 

2.87 

1691 

1.67 

1611 

2.66 

1531 

2.01 

1770 

1.31 

3.57 

2.84 

1690 

1.79 

1610 

2.15 

1530 

2.19 

1769 

1.30 

3.60 

2.84 

1689 

1.80 

1609 

2.31 

1529 

2.10 

1768 

1.27 

3.72 

2.85 

1688 

1.80 

1608 

2.44 

1528 

2.08 

1767 

1.43 

3.40 

2.93 

1687 

1.95 

1607 

2.07 

1527 

1.95 

1766 

1.37 

*3.08 

•2.72 

1686 

1.71 

1606 

1.80 

1526 

1.85 

1765 

1.33 

1085 

2.00 

1605 

1.81 

1525 

1.94 

1764 

1.44 

1684 

1.78 

1604 

2.09 

1624 

1.93 

1763 

1.33 

1683 

2.19 

1603 

1.72 

1523 

1.99 

1762 

1.66 

1682 

2.03 

1602 

1.83 

1622 

1.96 

1761 

1.44 

1681 

2.00 

1601 

1.54  i 

1521 

1.71 

*  The  portions  of  these  columns  between  the  stars  are  based  not  only  on  the  hgures  here  given  in  the  columns  to  the  left,  but  also  on  portions  of  groups 
II  and  III,  which  are  here  omitted  because  they  are  based  on  a  number  of  trees  smaller  than  the  number  indicated  at  the  top  of  the  first  part  of  this  table. 


330  Table  J. — Errors  of  Ring  Counting  in  northern  Arizona  Pines. 

The  minus  sign  indicates  that  the  tree  made  no  ring  in  this  particular  year.  A  plus  sign  indicates  an  extra  ring.  D  after  the  date 
signifies  that  in  the  straight-away  count  this  ring  was  noticed,  but  was  considered  a  double,  and  hence  was  reckoned  with  one  of  the 
adjacent  years.  The  brackets  mean  that  the  ring  was  actually  measured  but  still  considered  a  double  belonging  with  its  neighbor. 

[Table  compiled  by  A.  E.  Douglass.] 


No.  of 

Year  sup- 

No.  of 

Age  in 

years  for 
which 

posed  to  be 
1700  A.  D. 

Errors  in  last  100  years. 

Errors  in  next  to  last  100  years. 

Errors  in  portions  dating  back  more 

section. 

years. 

identifica- 

than  200  years. 

tion  is 
complete. 

count. 

VII 

212 

200 

1705 

-1892,  -11828],  -[1821],  -[1813] 
-[1821] 

-1902,  -1893,  -1892,  -1891, 

-[1747D] 

VIII 

333 

322 

1701 

IX 

409 

406 

1714 

-[1781],  -1772,  -1752,  -[1747], 

-[1669],  -[1631],  -[1584],  -[1541], 

-1890,  -[1885],  -1878D,  -1821, 
-1813 

-[1734] 

-[1531] 

X 

328 

322 

1703 

-1821 

-[1751],  -[1734] 

XI 

.326 

320 

1718 

15  errors  between  1910  and  1870 

-1608,  -[1599] 

-1863,  -1846,  -1813 

XII 

528 

520 

1702 

-[1821] 

-1751D 

-[1653],  +1652K.  +1650M, 

-1640D,  -1584,  -1583,  +1553JS. 
+1562^,  -1541,  -1531,  -[1490], 
-[1463],  -1462,  -[1433],  -1420D, 
-1418D,  -1412 

XIII 

520 

518 

1710 

-[1903],  -[1846],  -[1844],  -1841D, 

-1752 

-1659,  -1653,  -1632,  -1600, 

-1839,  -1821,  -1819,  -1817, 

-1584,  -1583,  -[1679],  -1S65* 

-1813 

-1564*,  -1531,  -[1521],  -1481D, 
-[1462] 

XIV 

331 

330 

1706 

-1873,  -[1846],  -[1821],  -[1819] 

-[1781],  -1770D 

+1684H.  -1584,  -1583 

XV 

363 

350 

1708 

+1907,  -1903D,  -1893,  -1892, 

-[1751],  -1734D 

-1891,  -1890,  -1882D,  -1879D, 
+1833H.  -1821 

XVI 

378 

377 

1706 

+1907,  -1846,  -1844,  -1821, 

-1813 

-1751,  -[1747],  -[1734] 

-1669,  -[1653],  -1631D 

XVII 

413 

407 

1707 

-[1903],  -[1901],  -[1821],  -1813 

+1802K.  -1788,  -[1772], 

-1751,  -[1734] 

-[1669],  -[1653],  -[1631] 

XVIII 

217 

212 

1700 

-1817 

+1773H 

XIX 

243 

237 

1700 

XX 

300 

1730 

-1903D,  -1901D,  -1896,  -1895, 
-1894,  -1893,  -1892,  -1891, 

-1807,  -1801,  -[1788],  -1781, 
-1778,  -1770,  -1760,  -1758, 

-1890,  -1846,  -1844,  -1841, 
-1838,  -1834,  -1821,  -1819, 
-1817,  -1816,  -1813D 

-1751,  -[1747],  -1734 

XXI 

267 

260 

1702 

-1821 

-1751 

+1649>^ 

XXII 

345 

344 

1705 

-1846D,  -[1821],  -[1819] 

-[1751],  -[1734] 

-1683D 

XXIII 

410 

408 

1717 

-1904,  -1903,  -1902,  -1901, 

-[1781],  -1751,  -[1747],  -1734 

-1669,  -1632,  -1599,  -1584, 

-1899,  -1896,  -1895,  -1894, 
-1893,  -1892,  -1891,  -1890, 
-1879D,  -1821 

-1583,  +1666)i,  -(15411 

XXIV 

349 

346 

1710 

-1846,  -1841,  -1821,  -1819, 

-1772D,  -1756,  -1761,  -1734 

-1814,  -1813D 

XXV 

350 

350 

1711 

-[1901],  -1895,  -1879,  -1878D, 
-[1841],  -1821,  -1814,  -1813 

+1784V4.  -1772D,  -1761, 
-[1747],  -1734 

-[1669],  -fl653],  -[1631],  -[1684] 

Average . . . 

348 

INDEX. 


A'ai  Sto  ruins,  63 

Abbott,  C.  G.,  cited,  4,  236,  246,  250  £f. 

Abbott  (Judge),  84 
Acacia,  21 

Accidents,  effect  upon  tree-growth,  124,  134 
Accumulated  moisture,  effect  on  tree-growth,  114,  164 
Africa,  asylum  of  Pliocene  life,  288 

pre-Devonic  glacial  deposits  in,  290,  291 
Age  of  trees,  corrective  factor  for,  124  ff. 

Agriculture,  effect  on  civilization,  220 
in  Arizon^9,  10,  12 
Chaco  Canyon,  80  f. 
lower  Santa  Cruz  Valley,  54 
northwestern  New  Mexico,  76  ff. 

Pajarito  Plateau,  91,  93 
tropics,  handicaps  of,  231  f. 

Yucatan,  180 
on  artificial  terraces,  60 
terraces,  68  ff. 

Agua  Caliente,  ruins  at,  52 
“Aguadas”  in  Yucatan,  177,  184 
Aguilera,  J.  G.,  100 
Ahau,  in  Maya  chronology,  227 
Ahpula,  Maya  chief,  228 
Alamo  San  Francisco,  ruins,  66 
Alamogordo;  fault  at,  38 
well  at,  38 
Alluvial  fans,  19 
Alps,  Miocene,  284 

Paleozoic,  278,  287 
Altar,  pottery  at,  65 

River,  length  of,  50 
Altitude,  effect  upon  civilization,  219 
America,  North  and  South,  united  in  Miocene,  284 
Amerinds  (see  Hohokam),  48 
Ammonites,  distribution  of,  in  Jurassic,  281 
Triassic,  280 

Angiosperms,  rise  of,  in  Lower  Cretacic,  282 
Upper  Cretacic,  283 

Animas  Dam,  70 

Animas  Valley,  ruins  in,  70  ff. 

Antelope,  sufferings  from  drought,  71 
Antillean  Mountains,  283 
Anti-pleions,  244  ff. 

Appalachian  Mountains,  278,  283,  287 
Arboreal  vegetation,  21 
Archseocyathinae,  275,  276,  291,  295 
Arches  in  Yucatan,  186 

Architecture,  as  a  means  of  determining  chronology,  226  ff. 
in  Yucatan,  183,  186 
of  Hohokam,  47,  53 

ruins  in  northwestern  New  Mexico,  77  ff. 
Pajaritan  Plateau,  83 
sequence  of,  among  Mayas,  229  f. 

Arctowski,  H.,  cited,  137,  244  ff, 

Arequipa,  changes  of  temperature  at,  247 
solar  constant  at,  246 
Aridity,  Lower  Devonic,  277 

relation  to  glaciation,  259 
Siluric,  ^7 

Arizona; 

Capacity  for  supporting  population,  50 
Climate  of,  9  ff.,  101 
Experiment  station,  50 
Rums  in,  47  ff. 

Scenery  of,  15  ff. 


Arrhenius,  cited,  234 
Artesa,  ruins  at,  61 

Asia,  climatic  changes  compared  with  America,  171  ff. 
Assyria,  compared  with  Mayas,  184 
Astronomical  knowledge  of  Mayas,  228,  229 
Atlantic  forests  of  Guatemala,  216  ff. 

Atmospheric  pressure  in  polar  regions,  206 
Australia,  latest  Proterozoic  glaciation  of,  269,  270,  291 
Azalea,  habitat  of,  141 
Azcapotzalco,  excavations  at,  97 
Aztecs,  architecture  of,  98 

migration  to  Mexico,  96 
ruins  of,  97 

Bacalar,  ruins  at,  229 
Bahada,  18  f.,  24  ff. 

At  Magdalena  Trinchera,  69 
Bakersfield,  rainfall  of,  157  f. 

Ball  court  in  Yucatan,  230 

Banana  plantations  in  Guatemala,  216  f. 

Bandai-San,  eruption  of,  250 
Bandolier,  A.  F.,  cited,  207  f. 

Baobab,  age  of, -139 
Barometric  pressure: 

Relation  to  changes  of  climate,  137 
storm  tracks,  191 
tree  growth,  171 
Barrel!,  J.,  cited,  23,  28,  235 

On  climatic  evidence  of  sediments,  273 
Basin  ranges,  15 

Batavia,  changes  of  temperature  at,  248 
Baul,  ruins  at,  219 
Beard’s  ranch,  ruins  at,  72 
Beasts  of  burden,  absence  among  Mayas,  187 
Beech,  conditions  favorable  to  growth,  134 
corrective  factors  of,  132 
ciuwe  of  growth,  133 
Bigelow,  F.  H.,  cited,  241 

Big  Trees  of  California  (see  Sequoia  washingtoniana),  131 

Biologic  evidence  as  to  climate,  275 

Black  color  in  sediments  as  evidence  of  climate,  273 

Blackwelder  (see  Willis),  271 

Blake,  cited,  91 

Blanceneaux,  F.j  cited,  217 

Blazer,  A.  M.,  cited,  45 

Boas,  F.,  cited,  97  ff. 

Bogoslof,  eruption  of,  251 

Bokkeveld  series,  290 

Bombay,  changes  of  temperature  at,  248 

Bonillas,  Y,  S.,  100 

Bonneville,  Lake,  37 

Compared  with  Otero  Basin,  38 
Bonney,  cited,  242 
Bonpland,  cited,  96 
Botanical  evidence  of  desiccation,  92 
Bovee,  Mr.,  53,  59 

Bowditch,  C.  P.,  cited,  214,  215,  227,  228 
Bridges,  land,  2^ 

British  Honduras: 

Density  of  population,  216 
Physical  features  of,  211  f. 

Brown,  H.,  cited,  55 
Bruckner,  E.,  cited,  4,  89,  118,  242 
cycles,  118,  140 

Buckman,  on  Tiiassic  ammonites,  280 
Bulawayo,  changes  of  temperature  at,  247 


332 


INDEX. 


Bull  pine,  curve  of  growth,  133 
Buntsandstein,  268 
Burial  customs  of  Hohokam,  78 
Bush,  definition  of,  178 
in  Guatemala,  212 
relation  to  changes  of  climate^  190 

density  of  population,  180 
vegetation  in  Guatemala  and  Yucatan, 
218 

Buttresses,  effect  of,  on  tree  measurements,  155  f. 

Buzani,  ruins  at,  86  f.,  138 

Spanish  mission  at,  65,  86  f. 

Cababi,  pottery  at,  47 
O/AborcA  OS 

Caledonian  Mountains,  277,  286,  287 
Calendar  of  Mayas  (see  Chronology). 

Caliche  in  terraces,  24,  25 
California: 

Annual  distribution  of  rainfall,  141,  157  f. 

Climatic  changes  compared  with  Asia,  171  ff. 

Mexico,  207  ff. 

Monthly  distribution  of  rainfall,  159  ff. 

Rsdnfall  compared  with  England,  241 
Relation  of  tree  growth  to  sun-spots,  238 
Variations  of  temperature,  208 
Cambric: 

Climate  of,  270,  276 
Cool  period  in  Lower,  287 
Glaciation  in,  269 
Life  of,  276 

Mountain-making  in,  276,  287 
Campeche,  coast  of,  176 
ruins  in,  217 

Cafiada  del  Oro,  terraces  of,  25,  29 

Canada,  Proterozoic  glaciation  in,  272,  295,  296 

Canals,  ancient,  44,  46 

Canby,  H.  S.,  142 

Canoes  in  Mexico  City,  96 

Canyon  de  Chelly,  75 

los  Frijoles,  83  f.,  91 
Carbon  dioxide,  in  Upper  Carbonic,  278 
Carbonic  acid  theory  of  glaciation,  234,  235,  261,  289 
Carbonic,  Lower: 

Climate  of,  277 

Coal  in,  in  Arctic  region,  277 

Life  of,  277 

Mountain-making  in,  278 
Carbonic,  Upper: 

Carbon  dioxide  in,  278 
Climate  of,  278 
Floras  of,  278 
Insects  of,  278 
Life  of,  278 

Carnegie  Institution,  relation  to  investigation,  2 
Cascade  Mountains,  281 
Caspian  Sea,  as  basis  of  corrective  factor,  156 
Cattle,  economic  importance  to  Indians,  51 
raising  and  rainfall,  14 

in  Guatemala,  216 
relation  to  terraces,  33  \ 

Caves  of  Yucatan,  176  f. 

Cavo,  cited,  207 
Cedars  of  Lebanon,  age  of,  139 
“Cenotes”  of  Yucatan,  176  f.,  184 
Census,  at  El  Paso,  138 

Ceremonial  platforms  (see  Religious  structures),  68 
Cerra  Tortuga,  ancient  graves,  65 
Ceylon  compared  with  Maya  civilization,  223 
Chaco,  Canyon,  ruins  in,  17,  75,  79  ff. 

Chamberlin,  T.  C.,  cited,  23,  234 

and  Salisbury,  on  Permic  interglacial  warmer 
climates,  268 

Changes  of  climate  (see  Climatic  Changes) 

Chapman,  K.  M.,  cited,  44,  82,  84 
Chapultepec,  97 


Charco  del  Yuma  ruins,  53  ff. 

Chaves  Canyon,  76 
Chewing  gum,  from  zapote  tree,  186 
Chiapas,  ruins  in,  186,  217 
Chichen  Itza: 

Date  of,  227,  228 
Ruins  of,  183,  229 
“Chicleros,”  186 
Chihuahua,  terraces  in,  99 
Children,  ^ect  of  malaria  on,  181,  220 
China  compared  with  Mayas,  184,  185 

Proterozoic  glaciation  in,  271,  293,  294,  295 
tilUtea  of,  269,  271,  272,  294,  295 
Chinese  Turkestan  compared  with  Arizona,  57 
Chiquimula  River,  terraces  of,  213 
Chronology  and  climate,  3 
Of  ancient  America,  88,  90 
Maya  ruins  at  Copan,  214 
Mayas,  227  f. 

Cisterns  in  Yucatan,  184  f. 

Civilization,  causes  of  rise  and  fall,  226 

conditions  of  high,  in  past  and  present,  219  f. 
measures  of  greatness  of,  184 
Civilizations,  succession  of  (see  Culture,  stages  of),  85 
Cliff-dwellers,  relation  to  topography,  17 
Cliff-dwellinp,  75 

Of  Pajaritan  Plateau,  83 
In  southern  New  Mexico,  71 
Cliffs  of  arid  regions,  17 
Climate: 

And  history,  sununary  of  theory,  232 

human  character  in  equatorial  regions,  181  f.,  221 
topographic  changes,  289 
Arid,  269,  277,  286,  288 
Cambric,  270,  276 
Chart  of  changes,  285 
Cold  vs.  warm,  286,  288 
Devonic,  277 

Effect  upon  topography,  15  ff. 

Effects  of,  on  ocean,  279 
Eocene,  283 

Evidence  of  sediments  as  to,  273 
General  conclusions,  23,  288  f. 

instability  of,  235 
Glacial,  history  of  study  of,  265 
Insular,  288 
Jurassic,  281,  287 
Liassic,  280,  281,  286 
Lower  Carbonic,  277 
Cretacic,  282 
Miocene,  284 

Of  geological  times,  257  ff. 
land,  vs.  water,  287,  288 
New  Mexico,  Arizona,  etc.,  9  ff. 

Ordovicic,  276,  277,  287 
Permic,  279 
Siluric.  276,  277,  286 
Triassi^  280 
Upper  Carbonic,  278 

Cretacic,  283,  286,  288 
Climatic  changes: 

According  to  Hewett,  Henderson,  and  Robbins,  90  ff. 
Botanical  evidence  in  New  Mexico,  92 
Cause  of,  4,  5,  233  ff. 

Co-ordination  in  different  parts  of  the  world,  139  ff. 
Crustal  deformation  as  cause  of,  257  ff. 

Dates  of,  43 

Effect  on  man,  48,  92,  210 

upon  se^onal  precipitation  in  Mexico,  207  ff. 
Effecte  upon  history  of  America,  88  f.,  225 
In  Asia  compared  with  America,  90,  171  ff.; 
California,  evidence  of  recent  changes,  153 
Mexico,  95  ff. 

compared  with  California,  207  ff. 
Limitations  in  method  of  measuring  by  tree  growth, 
152 


INDEX. 


333 


Climatic  changes — continued: 

Magnitude  of  changes  of  rainfall,  167 
Meteorological  explanation  of,  236 
Nature  of,  1 

Of  geological  times,  257  ff. 

Pulsatory  vs.  gradual,  88 
Recorded  in  Piedmont  deposits,  19 
Relation  of  gypsum  dunes,  41  ff. 

recent  to  glacial,  206 
to  cyclonic  storms,  170 
diseases,  224 
Otero  strands,  39  ff. 

Sequoias  as  standard  for  measurement  of,  141  ff. 
Solar  hypothesis  of,  233 

Summary  of  theory  in  respect  to  United  States,  87  ff. 
Ts^es  of,  233  t. 

Climatic  curve,  liability  to  error,  170  f. 
cycles,  117  ff.,  233 
theories,  methods  of  testing,  95,  175 
zones,  Jurassic,  281 

shifting  of,  172,  189  ff. 

Cloudcroft,  44 
Clough,  H.  W.,  cited,  118 
Cloverdale,  N.  Mex.  70,  71 
Coal  Measures,  life  of,  277,  278 
Upper  Carbonic,  278 
Coast  Range,  141 

redwood,  curve  of  growth,  133 
Coastal  plain  of  Yucatan,  176 
Coborca,  87 

Cocospera,  terraces  of,  26 
Colds,  danger  of,  220 
Coleman,  A.  P.,  cited,  23 

On  Proterozoic  glaciation  in  Can.ada,  295,  296 
Colima,  eruption  of,  251 

Color  of  sediments,  as  evidence  of  climate,  273,  274 
Colorado  Canyon,  15 
Communal  houses,  Animas  Valley,  71 
near  Thoreau,  76 
Comovavi  Moimtains,  62 
Conservation  factor  in  rainfall,  165  ff. 

Consumption  compared  with  malaria,  220 
Continental  deposits: 

Lower  Cretacic,  282 
Proterozoic,  275 
Upper  Cretacic,  282 
Converse  Basin,  142 
Cool  period.  Lower  Cambric,  287 
Jurassic,  287 
Ordovicic,  287 
Triassic,  287 ; 

Copan,  date  of  ruins  at,  214  f.,  227 
ruins,  218,  229 
terraces  of,  213  ff. 
vegetation  of,  216 
Cope,  cited,  91 
Copper  in  Yucatan,  187 
Coral  reefs,  Jurassic,  281 
Triassic,  280 

Corn  crop  of  United  States,  243  ff. 

Corn,  good  years  vs.  bad,  81 

method  of  raising  in  Guatemala,  222 
Yucatan,  180 

Correction  for  errors  in  counting  rings,  144  ff. 

flare  and  buttresses,  154  ff. 
longevity  in  deciduous  vs.  coniferous  trees, 
132 

Sequoia  washingloniana,  151 

Corrective  factor: 

According  to  Caspian  Sea,  156 
For  absence  of  rings,  146  ff. 

age,  applied  to  yellow  pine,  129  f. 
of  trees,  124  ff. 

change  in  number  of  trees,  127  f. 
longevity,  127 

applied  to  yellow  pine,  131  f. 


Cortez,  96 
Covered  Wells,  62 
Creosote  bush,  21 
Cretacic,  Lower: 

Chmate  of,  282 
Faunas  of,  282 
Reef  corals  in,  282 
Rise  of  Angiosperms  in,  282 
Seasonal  changes  in,  287 
Cretacic,  Upper: 

Angiosperms  in,  283 
Climate  of,  283,  286,  288 
Great  mortality  in,  283 
Mountain-malang  in,  283,  288 
Reef  corals  in,  283 
Wood  with  rings  in,  282 
Critical  periods,  286,  287 

and  volcanism,  287 
Crocker’s,  rainfall  at,  159 
Croll,  theory  of  glaciation,  234 
Crops,  size  in  past  vs.  present,  81 

Crustal  deformation  as  cause  of  climatic  changes,  5,  255  ff. 
movements  in  Guatemala,  213 

relation  to  glaciation,  257  ff. 
Cuautitlan  River,  change  of  course  of,  97 
Cultivated  plants,  escape  of,  61 
Culture: 

Distribution  of,  in  Guatemala,  225  ff. 

Stages  of,  in  New  Mexico,  75  ff.,  82  ff.,  84 
Cummings,  cited,  91 
Curd,  J.  W.,  cited,  138 
Cutter,  V.  M.,  cited,  217 
Cycles,  barometric,  118 
of  climate,  117  ff. 

Cyclones  related  to  sun-spots,  237  ff. 

Cyclonic  storms,  in  New  Mexico,  9,  11 
Yucatan,  190 

relation  to  changes  of  climate,  190  ff. 
growth  of  Sequoias,  170 
magnetic  variations,  204  f. 
variations  in  tracks  of,  193  ff. 
vs.  monsoon  type  of  rainfall,  137 

Dalton,  78 

Dam  at  Animas,  70 

Dark  ages  of  Maya  History,  229  f. 

Dates  of  climatic  changes,  43 

Datil  National  Forest,  128 

David,  T.  W.,  cited,  242 

Davis,  W.  M.,  cited,  15,  23 

Death  rate  in  England  vs.  tropical  countries,  221 

Deccan  lava  flows,  283 

Defense,  art  of,  in  relation  to  climatic  changes,  56  f. 
Defensive  works  (see  Forts),  80 
Deforestation  in  Mexico,  96 
Density  of  population: 

In  British  Honduras,  216 
Guatemala,  216  ff. 

Depopulation  in  relation  to  climatic  changes,  57 
Desert  conditions  of  the  southwest,  21 
Laboratory,  52 
pavements,  24 

Desiccation  (see  Climatic  changes;  Rainfall),  92 
Devonic: 

Climate  of,  277 
Coal  in,  277 
Life  of,  277 
Mountain-making,  277 
Volcanoes  in,  287 
Dikes  in  Mexico,  96,  207  ff. 

Dillonwood,  curves  of  annual  tree  growth,  161 
rainfall  of,  158 

Diseases,  effect  of  introduction  in  tropics,  223  f. 
of  Guatemala,  218 
tropical  lands,  220 
Disemboque,  66 


334 


INDEX 


Double  rings  in  Sequoia  washingtoniana,  146 
Douglass,  A,  E.,  3,  6,  101  ff.,  123,  124,  128,  135,  140,  157, 
163,  238 

Fonnma  for  tree  growth,  160,  166 
Doudass  fir,  curve  of  growth,  133 
Drinking-water: 

Ancient  supply  of,  54,  57  f.,  62  f.,  72  f.,  79  f. 

At  Gran  Quivira,  86 
Drought  in  Animas  Valley,  71  f. 

Central  New  Mexico,  86 
northwestern  New  Mexico,  81 
Otero  Basin,  73 
years  of,  54,  61 
Dry  farming,  50,  60 
In  ancient  times,  69 

northern  New  Mexico,  81 
Dunes  of  gypsum  in  Otero  Basin,  40  ff. 

Movement  of,  40 
Dunwoody,  H.  H.,  cited,  192,  193 
Durango,  terraces  in,  99 

Dust  in  atmosphere,  effect  on  tempCTature,  250  ff. 

solar  atmosphere,  as  climatic  factor,  274,  275 
Dysentery  in  Tropics,  221 

Earth,  cooling  of,  289 

nature  of  interior  of,  265 
periodical  changes,  of  shape  and  size,  289 
shrinkage  of,  289 
Eberswalde,  tree  growth  at,  120  f. 

Egypt  compared  with  Mayas,  184 
relation  to  Mayas,  185 
Ekholm,  N.  G.,  cited,  242 
Elemax  ruins,  186 
£1  Paso,  famine  at,  138 
Emi^ation  from  Europe  and  rainfall,  89 
Empire  ranch,  25 
Rainfall  of,  60 

England,  rainfafi  compared  with  California,  241 
relation  of  crops  to  rainfall,  241 
Eocene,  climate  of,  283 

volcanism  in,  287 

volcanoes  in,  in  Rocky  Mountains,  283 
Eolian  deposits  of  Otero  Ba^,  40  ff. 
erosion  at  Disemboque,  67 
in  Otero  Basin,  73 
relation  to  desert  pavements,  24 
Epochs  of  early  American  civilization,  88 
Equatorial  rains  in  Yucatan,  177 
Erosion  in  dry  regions  vs.  wet,  16  f. 

Escuintla,  218 

Esmeralda,  186 

Espita,  rainfall  of,  178 

Europe,  emigration  from  and  rainfall,  89 

“Exploration  in  Turkestan,”  23,  26i  90 

“Fats,”  243 

Fault-block  mountains,  18 
Faunas: 

Jurassic,  281 
Lower  Cretacic,  282 
Festival  of  summer  rains,  59 
Fevers,  effect  on  civilization,  220  f. 

Fewkes,  J.  W.,  cited,  49,  91 
Fire-places  in  ruins,  66,  73 
Flagstaff,  Ariz.,  tree  measurements  at,  102  ff. 
rainfall  of,  13 

Flare  of  trunk,  effect  upon  tree  measurements,  154  f. 
Flood,  tradition  of,  at  Magdalena,  68 
Floods  in  Mexico,  96  ff. 

periodic,  in  North  America,  288 

times  of  occurrence  in  Santa  Cruz  Valiev,  54 

Floras: 

Jurassic,  281 
Triassic,  280 
Upper  Carbonic,  278 
Fluvial  deposits  of  Mexico  City,  98  ff. 


Forbes,  R.  H.,  cited,  24,  44,  50,  51,  53,  60,  106,  110 
Forest,  compared  with  jungle,  178 

fires,  effect  upon  tree  growth,  134 
Service  of  United  States,  123,  131,  139 
Forests  and  civilization,  186 

Humboldt’s  view  of,  in  Mexico,  96 
of  Guatemala  and  Honduras,  211 
Yucatan,  176, 179 
relation  to — 

agriculture  in  Guatemala,  221  f. 

in  tropics,  181 
changes  in  climate,  190 
density  of  population,  180 

of  population  in  Guatemala,  217 
ruins,  190 
ruins  in,  186 

Formula  for  redfucing  tree  growth  to  rainfall,  115,  166 
rainfall  to  tree  growth,  113  f. 

Fort  Lowell,  ruins  near,  52 
Forts,  ancient,  51,  52,  56,  80 
at  Nolik,  ^ 

Satan’s  Canyon,  77 
location  in  respect  to  rivers,  74 
Whipple,  Arizona,  105 
(See  also  Walls  for  defense.) 

Fowle,  F.  E.  cited,  236,  246,  253  ff. 

Free,  E.  E.,  cited,  37,  41  f.,  138 
Fresno,  rainfall  of,  157  f. 

Frosts  in  Arizona,  9 

Fruit  and  frosts  in  Arizona,  9-10 

Gaisa  formation,  269,  270,  271,  292,  293 
Gallup,  N.  Mex.,  76 
Gamio,  M.,  cited,  97 
Gangamopteris  flora,  279 
Gardner’s  Canyon,  ary  farming  in,  60 
terraces  of,  25 

Geikie,  on  Torridonian  glaciation,  272 
General  Grant  National  Park,  142 
Germany,  tree  growth  in,  120  f. 

Relation  to  sun-spots,  238 
Gibbon’s  Ranch,  ruins  at,  59 
Gila  National  Forest,  128 
River,  terraces  of,  26,  28 
Valley,  climate  of,  9 
Gilbert,  G.  K.,  cited,  23,  37,  235 
Glacial  deposits,  pre-Devonic,  in  Africa,  290 
period,  cause  of,  5 

complexity  of,  256 

probable  reduction  of  temperature  in,  242 
relation  to  recent  climatic  changes,  206 
small  climatic  cycles,  233  f . 
terraces,  35  f. 

periods  in  early  geologic  times,  256 
Glaciation: 

Cambric,  269 
Devonic,  269 

Earliest  Proterozoic,  272,  285,  286,  295,  296 
Latest  Proterozoic,  270,  271,  285,  291,  292,  293 
Localization  of,  234,  255  f. 

Permic,  267,  268,  279,  284,  285,  286,  287 
Pleistocene,  266,  284 
Pre-Devonic,  287 
Proterozoic — 

In  Canada,  272,  273,  295,  296 
China,  271,  272.  293,  294,  295 
Norway,  270,  271,  292,  293 
Relation  to  aridity,  258 

crustal  movements  and  mountain-making, 
256  ff. 

Theories  of,  206  f.,  234 
Torridonian,  272,  285 

Undated  Proterozoic,  271,  272,  285,  293,  294,  295 
Glossopteris  flora,  268 
Gran  Quivera: 

Abandonment  of,  138 


INDEX. 


335 


Gran  Quivera — continued: 

Ruins,  85  f. 

Grand  Wash,  terraces  of,  26 
Gravel  deposits  of  Arizona,  18  f. 

character  of,  24  f. 
depth  of,  19 
Mexico  Cit3',  98  ff. 

Graves,  H.  S.,  3,  123,  128 
Graves  of  Hohokam,  65 

Gray  color  in  sediments  as  evidence  of  climate,.273 

Gray,  E.  M.,  cited,  80 

Grazing,  effect  on  vegetation,  21 

Great  Valley  of  Calilornia,  rainfall  of,  157  f. 

Greece,  malaria  in,  220 

Greeks  compared  with  Mayas,  184,  187 

Greene,  Colonel,  58 

Gregorian  calendar  compared  with  that  of  Mayas,  229 

Grinding-holes,  55 

Griquatown  series,  271 

Ground  water,  level  of,  at  Charco  Yuma,  57 

Growing  season,  length  of,  in  Sierras,  170 

Growth  rin^,  in  Permic  trees  (see  Tree  growth),  279 

Guarda  Viejo  ruins,  218 

Guatemala: 

Agriculture  in,  221  f. 

And  the  highest  native  American  civilization,  21 1  f. 
Belts  of  vegetation  in,  216  f. 

Crustal  movements,  213 
Density  of  population,  216  ff. 

Diseases  of,  218,  219 
Distribution  of  population  in,  215  ff. 

Forest  zone  of,  216  ff. 

Highlands  of,  218 
Mountains  of,  218 
Pacific  Belt,  218 
Physical  features  of,  211  ff. 

Rums  in  highlands,  218 
Terraces  in,  212  ff. 

Guatemalans,  character  of,  218 
Gulf  of  California,  old  shore,  66 

Gulf  Stream,  effects  on  distribution  of  temperature,  248  f . 
Gypsum  dunes  of  Otero  Basin,  39  ff. 

Handlirsch,  on  Liassic  insects,  281 
Hann,  J.,  cited,  237,  241 
Harrison,  65,  67,  68 

Hatch  and  Corstorphine,  on  glacial  deposits  of  Africa,  291 
Head  form  of  Indians,  85 

Health,  conditions  of,  in  Guatemala,  211,  212,  217 
Hearths  (see  Fireplaces),  73 

Heat,  amount  necessary  to  produce  other  climatic  phe¬ 
nomena,  241  ff. 
effect  on  civilization,  220  f. 

Henderson,  J.,  cited,  90 
Henequen,  182 
Hermoso,  ruins  of,  80 
Hewett,  E.  L.,  cited,  84,  90,  91 

Hierod3q)hics  among  Mayas  (see  Chronology),  185, 219, 226 
Himalayan  Mountains,  Miocene,  284 
Hinderer,  C.  H.,  105,  106 
History  and  climate,  4 

of  early  America,  reconstruction  of,  88  ff. 

New  Mexico  in  relation  to  rainfall,  138 
Hobbs,  W.  H.,  cited,  205 
Hoffman,  cited,  91 
Hohokam: 

Conditions  of  life  among,  48  ff. 

Customs  of,  67  f. 

Definition  of,  48 

Food  of,  48,  67 

Handicaps  of,  49 

In  Southern  New  Mexico,  70  ff. 

Migrations  of,  49 
Mobility  of,  74 

Relation  to  Pueblo  Indians,  85 
Holmes,  W.  H.,  cited,  91 


Honduras,  Gulf  of,  213 

ruins  in,  213  ff. 

Hopi  Indians,  75 
Hough,  cited,  49 
Houses  of  Hohokam,  47,  53 

Howchin,  on  Proterozoic  glaciation  in  Australia,  291 
Hrdlicka,  A.,  cited,  85 
Humboldt,  A.  von,  cited,  96,  208 
Ranges,  281 

Hume-Bennett  Lumber  Company,  142,  162  f. 

Hume,  California,  142 

curves  of  annual  tree  growth  at,  162  f. 
rainfall  of,  158 
sequoias  at,  144 
Humphreys,  W.  J.,  cited,  251 

On  dust  in  solar  atmosphere,  274,  275 
volcanic  dust,  274,  275,  286 
Hunting,  relation  to  Hohokam,  79 
Hyper-pressure,  243 
Hypo-pressure,  243 

Idaho,  growth  of  yellow  pine,  135  f. 

rainfall  contrasted  with  New  Mexico,  136  f. 
Iddiugs  on  tillites  of  China,  272,  294,  295 
India,  compared  with  Arizona,  9,  10 

comparison  of  climate  with  Arizona,  9 
glacial  deposits  in,  271 
Proterozoic  glaciation  in,  271 
Indian  Basin,  142 

encampments,  ancient,  72 
Indians,  ancient  (see  Hohokam),  48 
methods  of  agriculture,  51 
stage  of  culture  in  Yucatan,  176 
of  Yucatan,  179  ff. 

Indo-China,  compared  with  Maya  civilization,  223 
Insects,  effect  upon  tree  growth,  134 

great  changes  in,  during  Permic,  279 

Jurassic,  281 

Liassic,  281 

Triassic,  280 

Upper  Carbonic,  278 

Interglacial  climates,  conclusions  on,  284,  285,  289 
epochs,  256 
warm  climates: 

Permic,  268,  285 
Pleistocene,  266,  285, 

Proterozoic,  270,  285 
Intermediate  gypsum,  41  f. 

International  School  of  American  Archeology  and  Ethnol¬ 
ogy,  97 

Inundations  in  Mexico,  (see  Floods),  98  ff. 

of  Mexico  City,  208  f. 

Iron,  absence  of  among  Mayas,  187 
importance  of,  in  civilization,  184 
tools,  effect  upon  Indians,  51 
Ironwood,  21 

Irrigation,  abortive  attempts  at,  in  Arizona,  58 
ancient  methods  of,  81 
in  Santa  Cruz  Valley,  50 
natural  at  Rillito,  54 
possibility  of  at  Magdalena  Trinchera,  69 
relation  to  terraces,  33 
Izamal,  rainfall  of,  178 
ruins  of,  229 

Jarilla  Mountains,  ruins  among,  72 
Java,  compared  with  Maya  civilization,  223 
Jaynes,  ancient  population  of,  53 
ruins  at,  52 

Jeffrey  pine,  curve  of  growth,  133 
Jemez  Mountains,  83 

National  Forest,  128 
Plateau  (see  Pajarito  Plateau). 

Johnson,  W.  D.,  cited,  23 
Jones,  W.  H.  S.,  cited,  220 
Juivak,  pottery  at,  47 


336 


INDEX, 


Jungle  compared  with  bush,  178  f. 

and  forest,  179 
ease  of  livelihood  in,  222 
in  Guatemala,  212 

relation  to  agnculture  in  Guatemala,  221  f. 
changes  in  climate,  190 
distribution  of  population,  181 

Jurassic: 

Ammonites,  distribution  in,  281 

Climate  of,  256j  281,  287 

Climatic  zones  m,  281 

Cool  period  in,  287 

Faimas  of,  281 

Floras  of,  281 

Insects  of,  281 

Reefs  in,  281 

Kabah,  ruins  of,  183,  229 
Kadapah  system,  271 
Kaibab  Plateau,  16 
Kamas  Creek,  terraces  of,  26 
Kanab  Canyon,  26 
Karoo  formation,  267 
Karst,  relation  to  vegetation,  179 
of  Yucatan,  176 
Katmai,  eruption  of,  250,  251 
Katun,  in  Maya  chronology,  227 
Kem  Lakes,  157  f. 

Keweenawan  formation,  271,  286 

Kichankanab  Lake,  185 

Kin  Ya’a  ruins,  77 

Kiva  (see  Religious  structures). 

Klamath  Mountains,  281 

Knowlton,  on  Triassic  floras,  280 

Koppen,  W.,  cited,  4,  237 

Krakatoa,  eruption  of,  250,  251 

Kullmer,  C.  J.,  cited,  contribution  by,  192,  193  ff. 

Labna,  ruins  of,  183,  229 

Lacustrine  deposits  of  Mexico  City,  97  f. 

plain  of  Mexico  City,  97  ff. 

Lahontan,  Lake,  37 
Lake  at  Animas,  70 
Lakes  of  Guatemala,  211 
Mexico,  95  ff. 

Fluctuations  of,  compared  with  trees  in 
California,  207  ff. 

La  Luz,  fault  at,  38 
Land  bridges,  2^ 

climates  of,  288 

Lands,  periodic  flooding  of,  by  oceans,  286 
Lang  Mountains,  70 
Langhorn,  Mr.,  M,  55 
Langley,  cited,  4 
Laplacian  theory,  265 
Laramide  Revolution,  283 
Laziness  in  Yucatan,  180 
Lee,  W.  T.,  cited,  28 
Leiden  plate,  228 
Lias,  climate  of,  280,  281 
coal  of,  281 
insects  of,  281 
volcanic  activity  in,  280 
Liassic  climate,  256 
Life,  great  destruction  of,  287 

struggle  of,  under  glacial  climates,  266 
Life  thermometer,  287,  288 
Lime  habit,  beginning  of,  276 
LipaJian  era,  275 
Lockyer,  W.  J.  S.,  cited,  118,  120 
Longevity,  correction  for,  127 
Lowe,  cited,  91 
Lower  Huronian; 

Limestones  of,  275 
Tillites  of,  272,  296 


MacDougal,  D.  T.,  2,  12,  21,  25,  61,  65 
Magdalena  River,  teiraces  of,  26 
trincheras  of,  67  ff. 

Valley,  50 

Terraces  of,  29 

Magnetic  phenomena  and  solar  changes,  237 

variations,  relation  to  cyclonic  storms,  204  f. 
Mahogany  in  Guatemala,  216 
Maisk  ruins,  62 

Malaria,  effect  on  children,  181 

in  Guatemala,  216  ff.,  217 
ravages  of,  220  f. 

Malarial  fevers  in  forest  t)s.  bush,  181 

Man,  effect  upon  wowth  of  trees,  134 

Mancos,  cliff-dwelungB  at,  75 

Mathematical  relation  of  rainfall  and  growth,  113  ff. 

Mauritius  changes  of  temperature  at,  247 

Maya  civilization: 

Condition  at  Spanish  conquest,  184 
Compared  with  Assyria,  184 

China,  184,  185 
Egypt,  184 

Contrj^ted  with  Asiatic  civilization,  223 
Origin  of,  185 
Maya  chronicles,  226 
chronology,  227  f. 
history  and  climatic  changes,  225 

sources  of  knowledge  of,  226  f. 

Mayas: 

Ancient  civilization  of,  182 
Character  of,  179  f. 

Compared  with  Greeks,  184 

Contrast  of  civilization  with  that  of  Spaniards,  222 

Effect  of  cool  weather  upon,  210 

Handicaps  of,  187 

Hieroglyphics  of,  185,  219,  226 

Location  of,  175 

Mental  attributes  of  ancient,  187 
Ori^ality  of,  182  ff. 

Racial  features  of,  219 
Resemblances  of  modem  and  ancient,  183 
Water  simply  of,  177 
McAdie,  M.  G.,  cited,  159 
Merida: 

Rainfall  at,  178,  189 
Wealth  of,  182 
Windmills  at,  177 
Yellow  fever  at,  181 
Mesa  Verde,  17 
Mesas,  origin  of,  17 
Mescalero  Indian  agency,  45 
Plateau,  37 
Mesquite  trees,  21 
Age  of,  73 

Mestizos  of  Yucatan,  179 
Mexico: 

As  a  test  case,  95  ff. 

City,  evidences  of  changes  of  climate,  95 
founding  of,  96 
inundations  of,  208 

Climatic  changes  compared  with  California,  207  ff. 
Dikes  of,  207  ff. 

Effect  of  climatic  changes  on  seasonal  precipitation, 
208  ff. 

Ruins  of  northern,  65 
Meldrum,  cited,  237 

Meteorological  explanation  of  climatic  changes,  236 
Migrations  and  changes  of  climate,  88 
desiccation,  92 
rainfall,  89 

Miller,  H.  E.,  cited,  142 
Milo,  rainfall  of,  159 
Mindeleff,  cited,  44,  49,  56,  91 
Miocene: 

Alpine  mountains  in,  284 
Climate  of,  284 


INDEX. 


337 


Miocene — continued 

Elevation  of  mountains  in,  284 
Flora  of,  283  , 

Himalayan  Mountains  in,  284 
North  and  South  America  united  in,  284 
Miotherm  periods,  288 
Mokelunme  Hill,  rainfall  of,  159 
Mogollon  Escarpment,  15 
Moisture,  effect  on  diseases  in  tropics,  220  f. 

Moki  Indians,  relation  to  Hohokam,  48 
Monsoon  desert,  21 

Monsoon  vs.  cyclonic  type  of  rainfall,  137 
rains,  effect  on  vegetation,  22 
winds,  effect  on  distribution  of  temperature,  248 
Monsoons,  compared  with  winds  of  United  States,  9, 
10,  11 

Monterey,  California,  rainfall  of,  159 
Mexico,  terraces  near,  100 
Montezuma,  96 

Spring,  86 

Month  of  beginning  annual  means  of  rainfall,  110 
Monthly  Weather  Review,  95 

distribution  of  rainfall  in  California,  159  ff.  (See 
Seasonal  distribution.) 

Morley,  cited,  228 
Morrison,  cited,  91 

formation,  282 

Motagua  River,  terraces  of,  212  f. 

Motul,  rainfall  of,  178 
Moulton,  F.  R.,  cited,  23 
“Mountain  cultme”  of  Mexico,  98 
Mountain-making : 

And  cold  climates,  286 
volcanic  activity,  286 
In  Cambric,  276,  287 
Carbonic,  278 
Devonic,  277 
Ordovicic,  276,  287 
Permic,  278 
SUuric,  277,  287 
Tertiary,  284 
Upper  Cretacic,  283,  288 
Relation  to  glaciation,  258  fif. 

Mountains,  effect  on  rainfall,  12 

of  Guatemala,  structure  of,  211  f. 
nature  of,  in  Arizona,  17  f. 

Nahua  influence  in  Guatemala,  219 
Naranjo,  location  of,  217 

National  Theater  of  Mexico,  effect  on  surface,  96 
Navajo  Indians,  76 

Agriculture  of,  77  ff.,  81 
Nelson’s  Ranch,  ruins  at,  57  j 
Neumayr,  on  climatic  zones  in  Jurassic,  281 
Nevada,  comparison  with  Arizona,  21 
Newburg,  cited,  91 
Newcomb^  cited,  4,  241 
New  Mexico: 

Climate  of,  9  ff. 

History  of,  in  relation  to  rainfall,  137 
Rainfall  contrasted  with  Idaho,  136  f. 

Ruins  in  northwestern,  75  ff. 

southern,  70  fif. 

Scenery  of,  15  ff. 

Nine  Mile  water-hole,  54 
Ruins  at,  52 
Nolik,  ruins,  62 

North  America,  periodic  floods  in,  288 
“Northers”  in  Yucatan,  177 

Norway,  Proterozoic  glaciation  in,  270,  271,  292,  293 

riPOQTlQ  * 

How  cooled,  279,  288 
Periodic  spread  of,  toward  equator,  289 
Spread  of,  in  middle  Cretacic,  282 
Temperature  of,  288 

23 


Old  Red  Sandstone,  277 
Supposed  tillites  in,  269 
Olympia,  Greece,  26 
Oraibi,  75 
Ordovicic: 

Climate  of,  276,  277,  287 
Cool  period  in,  287 
Life  of,  276 
Limestones  in,  276 
Mountain-making  in,  276,  287 
Reef  corals  in,  276 
Organ  Range,  38 
Orientation  of  ruins,  59 
Otero  Basin,  description  of,  37 
ruins  of,  72  f. 

Soda  lakes,  description  of,  39 
fluctuations  of,  37 
Ouachita  Mountains,  278 

Pacific  Forests  of  Guatemala,  216 
Pajaritan  Plateau,  17 
Agricultiu’e  in,  83 

Changes  of  climate  according  to  Henderson  and  Rob¬ 
bins,  91 

Description  of,  83 
Ruins  of,  82  ff. 

Palenque,  location  of,  217 
ruins,  186,  229 
Paleometeorology,  255 
Paleozoic,  Alps  in,  278,  287 
glaciation,  256  fif. 

“Palestine  and  Its  Transformation,”  171 

sand  dunes  compared  with  those  of  New  Mexico, 
41 

Palo  verde  tree,  21 
Age  of,  34 

Pantano  Wash,  terraces  of,  25 
Panteleon,  ruins,  219 
Papago  Indians,  61  f.,  65 
At  Buzani,  87 
Traditions  of,  67 

Papaloapam  River,  terraces  of,  100 
Pel6,  eruption  of,  251 
Penck,  A.,  cited,  242 
Pepper,  cited,  82 

Periodic  flooding  of  lands  by  oceans,  286 
Periodicity  of  glaciation,  286 
Permian  glaciation: 

Causes  of,  257 

Contrasted  with  Pleistocene,  234,  257  f. 

Permic: 

Climate  of,  279 
Floras  of,  279 

Glaciation,  in,  267,  279,  284,  285,  286,  288 
Great  changes  in  insects  of,  279 
Growth  rings  in  trees  of,  279 
Interglacial  warm  climates  in,  268,  285 
Mountain-making  in,  278 
Persia,  comparison  with  Arizona,  21,  32 
Peten,  forests  of,  ruins  of,  216  ff. 

Peto,  rainfall,  178 
vegetation,  179 
Phoenix,  climate  of,  9 
Piedmont,  deposits  of,  17 

as  records  of  the  past  climate,  19 
of  Otero  Basin,  38 
gravels  of  Otero  Basin,  38 
Piedras  Negras,  ruins,  229 
Pig  ranches  in  southern  New  Mexico,  71 
Pima  Indians,  relation  to  Hohokam,  48 
Pine  ridges,  216 

yellow,  curves  of  growth  of,  128  ff. 

Pines,  effect  of  desiccation  on,  92 

of  Arizona,  measurements  of  growth,  101  ff.  (See 
also  Yellow  pine;  Bull  pine;  Shortleaf  pine.) 
Guatemala,  211 


338 


INDEX. 


Plains  of  Guatemala,  211,  222 

subaerial  deposition,  16  f. 

Planetesimal  theory,  265 

Plateau  of  Guatemala,  218 

Plateaus  of  Arizona  and  New  Mexico,  15  ff. 

Pleistocene: 

Glaciation  in,  266,  284 

contrasted  with  Permian,  234 
Interglacial  warm  climates  in,  266,  285 
Pleions,  137,  244  £f. 

Pliocene,  Africa  an  asylum  in,  288 

elevation  of  mountains  in,  284 
Pliotherm  periods,  288 
Pocy,  cited,  237 

“Point  of  the  Tucson  Mountains,”  53,  55  ff. 

Polar  regions,  atmospheric  pressure  of,  206 
Pompeckj,  on  Triassic  ammonites,  280 
Population: 

Ancient  density  of,  82 
Density  of,  among  Hohokam,  61 

in  Pajaritan  Plateau,  84 
ruins,  52  ff. 

Distribution  in  Guatemala,  211,  212 
Former  density  of,  in  northwestern  New  Mexico, 
77  ff. 

Populist  party  and  rainfall,  89 
Port  Lobos,  ancient  graves,  65 
Portersville,  rainfall  of,  157  f. 

Potomac  formations,  282 
Pottery: 

Abundance  of,  at  Jaynes,  52 

in  Arizona  ruins,  47 
In  Plain  of  Mexico  City,  97  ff. 
terraces,  24 

Relation  to  terraces,  43  f. 

Two  types  in  Pajaritan  Plateau,  84  f. 

Pottery,  unusual  type  at  Nelson’s  Ranch,  58 
Precessional  theory  of  glaciation,  234 
Precipitation  (see  Rainfall). 

Pre-Devonic,  glacial  deposits  in  Africa,  286,  287,  290,  291 
Prescott,  cit^,  96,  97 

Prescott,  Ariz.,  tree  measiuements  at,  112  ff. 

trees  at,  105  f. 

Pretoria  series,  271 

Prices  of  wheat  in  England  compared  with  sun-spots,  239  ff . 
Progreso,  rainfall  at,  177 

vegetation  at,  178 

Proterozoic  cycles  of  sedimentation  in,  275 
glaciation,  256  ff. 

Earliest  in,  272,  285,  286,  295,  296 
In  Canada,  272,  273,  295,  296 
China,  271,  272,  293,  294,  295 
Norway,  270,  271,  292,  293 
Latest  in,  269,  270, 271,  285, 291,  292,  293 
Undated,  271,  272,  286,  293,  294,  295 
life  of,  275 
limestones  of,  275 

possible  warmer  interglacial  climates  in,  270, 
285 

Provo  River,  terraces  of,  26 
Pueblo  Alto,  ruins  of,  80 
Viejo,  ruins  of,  77 
Bonita,  double  occupation  of,  82 
ruins  of,  79 
del  Arroyo,  82 
Indians,  75.  (See  Indians.) 

Prosperity  at  coming  of  Spaniards,  138 
Rebellion  of  1680  A.D.,  86 
Relation  to  ancient  inhabitants,  85 
changes  of  climate,  138 
Pulsations  of  climate,  117  ff. 

“Pulse  of  Asia,  The,”  90,  156 
Pyrenees  Mountains,  284 
Pyrheliometer,  measurements  with,  251 

Quich5,  ruins,  218 


Quijotoa  Mountains,  62 
Quirigua,  location  of,  217 
ruins,  215,  229 
terraces  at,  213 

Rainfall: 

Agreement  with  tree  growth,  106 

And  tree  growth,  effect  of  seasonal  distribution,  164 

Amount  required  for  agriculture  in  Arizona,  54  f . 

At  Prescott,  108 

Effect  of  season  of,  upon  tree  growth,  132 
Compared  with  sun-spots,  119  f. 

Cyclonic  vs.  monsoon  types,  137 
Effect  of  excessive,  upon  tree  growth,  167 
on  civilization,  219 

upon  density  of  population  in  tropics,  189  f. 
Estimation  of,  by  the  growth  of  tre^,  101  ff. 

In  England  compared  with  California,  241 
Sierras  compared  with  Arizona,  157 
Yucatan,  177 

Local  variations  in  northern  Arizona,  102 
“Made-up  records,”  159 
Method  of  calculating  annual,  110 
Monthly  distribution  in  California,  159  ff. 

Of  Arizona  and  New  Mexico,  10,  11 
California,  157  ff. 

past,  numerical  relation  to  present,  167 
Opposed  phases  in  Idaho  and  New  Mexico,  136  f. 
Records  in  Arizona,  103 
Relation  to  European  emigration,  89 
Populist  party,  89 

Seasonal  distribution  and  thickness  of  tree  rings.  111  ff 
Winter  vs.  summer,  11-13 
Racial  afiBnities  of  ancient  Americans,  85 
Rains  (see  Monsoon  rains), 

Recknagel,  N.  B.,  cited,  128  f. 

Red  color  in  sediments  as  evidence  of  climate,  273,  274 
fir,  curve  of  growth,  133 
deposits,  significance  of,  256 
sediments  and  arid  climates,  286 

geologic  distribution  of,  273 
spruce,  curve  of  growth,  133 
Redwood  (see  Sequoia). 

Reef  corals,  Cretacic,  282,  283 
Devonic,  277 

Reef  limestones,  275,  276,  277,  280 
Religious  edifices,  58 
Of  Hohokam,  47,  53 
Religious  structures,  56,  59,  61,  68,  83 
In  Yucatan,  183,  186 
Reservoirs  at  Gran  Quivira,  86 
Indian,  62 
Retalhuleu,  218 

Rhone  Glacier,  effect  of  11-year  cycle  on,  242 
Rich,  J.  L.,  cited,  26 
Rillito,  deposition  at,  34 
rums,  52 
terraces  of,  25 
Rincon  Valley,  ruins  in,  60 
Rings  of  tree  growth,  101 

Conditions  favoring,  102  f. 

Cross-identification  of,  105  f. 

Difficulties  of  measurement,  143 
Doubled,  110  ff. 

Doubling  of,  105 
Dropping  of,  143 
Method  of  dating,  105 
Nature  of,  103 

Thickness  according  to  the  points  of  compass,  104 
Time  of  formation,  110 
Yearly  identification  of,  107  f. 

Rio  Grande,  terraces  of,  26 
Riordan,  T.  A.,  103 
Rivers,  variable  loads  of,  32 
Robbins,  W.  W.,  cited,  90 
Rocky  Mountains,  284 


INDEX. 


339 


Rocky  Mountains,  volcanoes  in,  in  Eocene,  283 
Roemer,  on  Lower  Cretacic  climate,  282 
Rogers,  T.,  cited,  239 

On  glacial  deposits  of  Africa,  290 
Rogers  and  Schwarz,  on  glacial  deposits  of  Africa,  291 
Romero,  cited,  96 

Rooms,  size  of,  at  Gran  Quivira,  86 
in  ruins,  77,  83 
Ross,  R.,  cited,  181,  220 
Roxbury,  formation,  267 
Ruins,  abandonment  of,  82 

abundance  of,  in  Arizona,  New  Mexico,  etc.,  47 
age  of,  73 

factors  determining  location,  80 
in  Guatemala  Highlands,  218 
northwestern  New  Mexico,  75  ff. 
location  of,  in  respect  to  agricultural  lands,  48 
nature  of,  in  Arizona,  47  ff. 
near  Mexico  City,  97  ff. 
of  southern  Arizona,  47  ff. 
the  Mayas,  175 
Yucatan,  183  ff. 
orientation  of,  59 
relation  to  terraces,  44 
Ruelaa,  S.,  54 

Russell,  F.,  cited,  37,  48,  50,  51,  69 

Sabino  Canyon,  ruins  at,  52 
Sacaton  grass,  72 
Sage  brush,  21 
San  Andreas  Mountains,  38 
San  Diego  rainfall  compared  with  sun-spots,  120 
San  Francisco,  California,  rainfall  of,  159 
Compared  with  sun-spots,  119  f. 

San  Francisco,  Sonora,  ruins  of,  66 
Sand  dunes  at  Disemboque,  66 

relation  to  agriculture  in  dry  regions,  81 
Mountains,  102 
Sanger,  rainfall  of,  158 
San  Juan  Teotihuacan  culture,  97  ff. 

San  Miguel  Amantula,  excavations  at,  97 

San  Pedro  Valley,  terraces  of,  26 

San  Xavier  Indian  Reservation,  erosion  at,  33 

ruins  at,  51 

Santa  Barbara,  rainfall  of,  159 
Catalina  Moimtains,  17 
Rainfall  of,  12 
Terraces  of,  25,  29 
Cruz  Mountains,  284 

Reservoir  Company,  58 
River,  length  of,  50 
terraces  of,  31 
recent  terraces  of,  33 
station,  58 

Valley,  drainage  of,  54 

former  density  of  population,  50  ff. 
present  population  of,  50 
terraces  of,  24,  29 

Lucia,  218 

Rita  Mountains,  dry  farming  among,  60 
terraces  of,  25 

Toma  River,  terraces  of,  213 
Satan’s  Canyon,  76  f. 

Savannas,  cause  of,  216 
Sawtooth  Mountains,  18,  58 
Sayal,  ruins,  229 

School  of  American  Archeology,  44,  83 
Scotland,  Proterozoic  glaciation  in,  272 
Schuchert,  Chas.,  cited,  5,  251,  255  ff. 

Contribution  by,  265  ff. 

Sea  shells  among  ruins,  67 

Seasonal  distribution  of  rainfall,  effect  on  tree  growth,  164 
Sediments,  climatic  evidence  of,  273 
Seibal,  location  of,  217 
ruins  of,  229 
Seler,  cited,  227 


Sequoia  sempervirens: 

Curve  of  growth,  133 

Formula  of  relation  of  growth  to  rainfall,  166 
Habitat  of,  141 

Sequoia  washingtoniana,  141  ff.,  142  f. 

Age  of  measured  trees,  146 
Corrective  factors,  144  ff. 

Curve  of  growth,  133 

Curves  of  annual  growth  compared  with  rainfall, 
161  ff. 

Dimensions  vs.  appearance  of,  142 
Distribution  of,  132 
Young  trees,  153 
Double  rings  in,  146 
Durability  of  wood  of,  143 
Dying  out  of  species,  153 
Habitat  of,  141 
Habits  of  growth,  151 
Importance  of  curve  of  growth,  141  ff. 

Interpretation  of  curve  of  growth,  157 
Nmnber  of  measurements,  143  f. 

Rate  of  growth  in  old  age,  151 
Relation  of  growth  to  season  of  precipitation,  151 
Seve  series,  270 

Shading,  effect  upon  tree  growth,  134  f. 

Shakayuma  (see  Charco  del  Yuma),  54  ff. 

Sharks,  distribution  of,  in  Paleozoic,  277,  278 
Shell  heaps  at  Disemboque,  67 
Shift  of  the  storm  track,  193 
Shifting  of  climatic  zones,  174 
Shortleaf  pine,  corrective  factors  of,  132 
curve  of  growth,  133 
Shreve,  F.,  cited,  73 
Sierra  Blanco  Mountains,  37 
Nevada  uplift,  281 

rainfall  of,  157  f. 

Sierrita  Mountains,  17 
Siluric: 

Aridity  in,  277 
Climate,  258,  276,  277,  286 
Life  of,  276 

Mountain-making  in,  277,  287 
Reef  corals  in,  276 
Volcanoes  in,  287 
Sisal  (see  Henequen),  182 
Smith,  on  Triassic  climate,  280 
Smith’s  Lake,  76 

Snow-fall,  effect  upon  tree  growth,  132 

in  polar  regions,  Hobbs’s  theory  of,  206 
Soil,  poverty  of,  in  tropical  forests,  222 
relation  of  depth  to  climate,  18 
Solar  and  terrestrial  temperature,  241  ff. 
constant,  246 

heat,  inequality  of  distribution  to  earth,  249 
hypothesis  of  climatic  change,  233 

summary,  251 

objections  to,  241  ff. 
radiation,  effect  of  volcanoes  on,  250  ff. 
measimed  variations  of,  236 
variability  of,  274,  275,  289 
Sonora,  climate  of,  9  ff. 
mins  of,  65  ff. 
terraces  in^  100 

Spaniards,  as  immigrants  in  Mexico,  180 

contrast  of  civilization  with  that  of  Mayas,  222 
effect  of  intermixture  with  Indians,  180 

rainfall  on  occupation  of  America,  138 
in  Yucatan,  180 

Spanish  Mission,  Buzani,  65,  86 

at  Gran  Quivira,  85 
Sparagmite  formation,  270 
Spinden,  H.  J.,  cited,  215,  227 

Spring  droughts,  effect  upon  size  of  rains  in  Arizona,  111 

Springs,  ancient,  72,  80,  91 

Spruce,  curve  of  growth,  133 

Stages  of  culture  in  New  Mexico,  75  ff.,  82  ff.,  84 


340 


INDEX. 


Staked  Plains,  15 
Stem  analyses,  123  ff. 

Stockton,  rainfall  of,  158 
Storm  frequency,  center  of,  193  f. 

track,  location  of  mean,  201 
shift  of,  193 

tracks  during  glacial  period,  206  f. 

Storms,  cyclonic,  relation  to  growth  of  sequoias,  171 
monthly  distribution  of,  194  ff. 
relation  to  sim-spots,  237  f . 
tracks  of,  191  f. 

(See  Cyclonic  storms). 

Strahan,  on  Proterozoic  glaciation  in  Norway,  292,  293 
Strands  at  Animas,  70 

Disemboque,  66 
of  Otero  Lake,  39  ff. 

Stump  analyses,  123  ff. 

Sugar  pine,  curve  of  growth,  133 

Sun  (see  Solar  radiation;  Solar  theory;  Sun  spots,  etc.), 
236 

Sunlight,  effect  upon  tree  growth,  134  f. 

Sun-spot  cycle  and  climate,  119  f. 

relation  to  climate,  4,  237 
Sun-spots,  and  terrestrial  temperature,  251  ff. 
compared  with  rainfall,  119  f. 

temperature,  120 
wheat  prices  in  England,  239  f. 
relation  to  cyclones,  237  f. 
storms,  237  f. 
temperatures,  237 
tree  growth,  238,  250 

Swinton,  A.  H.,  239 
Sykes,  G.,  62 

Syria,  comparison  with  Arizona,  21 
Tabasco,  ruins  in,  217 

Table  Mountain  series,  269,  277,  286,  287,  290,  291 
Talchir  formation,  267 

Tananarive,  Madagascar,  changes  of  temperature  at,  247 
Tanke  Verde,  ruins  at,  52 
Tasmania,  tillites  of,  268,  276 
Tecax,  rainfall,  178 

vegetation,  179 

Tectonic  theory  of  terraces,  28  ff. 

Temperature; 

Annual  march  of  mean  in  world,  253 
In  California  compared  with  sun-spots,  120 
Effect  of  solar  on  terrestrial,  241  ff. 
volcanoes  on,  250  ff. 

Fluctuation  of,  during  glacial  periods,  285 
Of  San  Diego  compared  with  sun-spots,  120 
Reduction  of,  287 

In  Glacial  period,  242 
Relation  to  sun-spots,  237 
Temples  (see  Religious  structures). 

“Tepetate,”  98,  100 
Terenate,  trinchera  of,  70 
For  agriculture,  68  ff. 

Terraces,  19  f. 

Artihcial,  for  agriculture,  60 
Climatic  hypothesis  of,  23  ff.,  31 
Correlation  of,  35 
For  agriculture,  68  ff. 

In  Guatemala,  212  ff. 

Mexico,  99  ff. 

Numbers  of,  35 
Of  rock  vs.  gravel,  29 
Tesuque,  44 
Tulerosa  Valley,  45  f. 

Verde  River,  44  _ 

Processes  of  formation,  28  ff. 

Relation  to  glacial  periods,  35  f. 

local  topography,  30 
man,  43  ff. 

Structure  of,  27 

Wide  distribution  of,  26  f.,  34 


Tertiary,  mountain-making  in,  284 
Tesuque,  N.  Mex.: 

Ruins  and  terraces,  44 
T5rpe  of  pottery,  44 
Tethys,  283,  287,  288 
Tewa  Indians,  44 

Abandonment  of  Jemez  Plateau,  91 
Tezcuco  Lake,  evidences  of  change  of  climate,  95  ff. 
Thompson,  E.  H.,  cited,  183,  210 
Thoreau,  76 

Thunder  showers  in  Arizona,  11 
Tikal,  location  of,  217 
ruins  of,  186,  229 
Tillites,  267 

Of  China,  269,  271,  272,  285,  294,  295 
Tills,  265,  267 
Tilting  of  earth’s  crust: 

Effect  on  terraces,  28  f. 

In  Mexico,  99 
“Times,”  El  Paso,  138 
Tolman,  C.  F.,  cited,  24 
Toltec  Station,  58 

Topographic  changes,  effect  of,  on  climate,  289 
Topography  in  relation  to  climate,  15  ff. 

Torquemada,  cited,  96,  97,  208 
Torridonian  formation,  272,  285 
Tortolita  Mountains,  17,  54 
Trade  winds,  effect  upon  malaria,  216 
Traditions  of  migration,  92 

Transcaspia,  sand  dunes  compared  with  those  of  New 
Mexico,  41 
Tree  growth: 

Accuracy  of  a  few  trees  as  measures  of  rainfall,  116 
individual  tree  records,  163 
Agreement  with  rainfall,  116 

And  climate,  limitations  in  use  of  method  in  climate, 
152 

Corrected  factor  for  longevity,  127 
Correction  for  age,  117 

change  in  number  of  trees,  127  f. 
Corrective  factor  for  age,  124  ff. 

Curves  for  trees  in  United  States,  133 
Degree  of  accuracy  in  measming  climate,  109 
Effect  of  accidents  upon,  124 

seasonal  distribution,  164 
500-year  curve  of,  115 
Formula  for  reduction  to  rainfall,  163 
In  Guatemala,  211 
Interpretation  of  curves  of,  140 
Mathematical  relation  to  rainfall,  113  ff. 

Methods  of  measuring,  103  f.,  123,  142  f. 

Numerical  relation  to  rainfall,  167 
Reasons  for  assigning  variations  to  climatic  causes, 
135  f. 

Relation  to  accidents,  132 

conservation  factor,  165  ff. 
season  of  precipitation,  151 
sun-spots,  238,  250 
volcanoes,  252 

Trees: 

Age  of  oldest  species,  139 
Annual  growth  of,  at  Prescott,  Ariz.,  107,  108 
As  a  means  of  chronology,  34 
measurers  of  chronology,  73 
Causes  of  variations  in  rate  of  growth,  123  f. 

Rate  of  growth  of  long-lived  vs.  short-lived,  126 
Triassic; 

Climate  of,  280 
Cool  period  in,  287 
Coral  reefs  in,  280 
Critical  for  ammonites,  280 
Faunas  of,  280 
Floras  of,  280 
Insects  of,  280 

Trincheras  of  Magdalena,  67  ff. 

Tuberculosis  compared  with  malaria,  220 


INDEX. 


341 


Tucson,  climate  of,  9,  10 
floods  at,  33 
Mountains,  18,  34,  54 
region,  terraces  of,  24 
rums  at,  51 
terraces  at  33  ff. 

Tulare  River,  142 
Sequoias  at,  144 
Tularosa  gypsum,  42 

terraces  of,  26 

Valley,  relation  of  terraces  to  man,  44  f. 

Tulip  poplar,  conditions  favorable  to  growth,  132 
corrective  factor  of,  132 
curve  of  growth,  133 
Tultitlan,  inimdation  of,  97 
“Tun”  in  Maya  chronology,  227 
Tunnel,  for  drainage  of  Mexican  Lakes,  97,  209 
Tuxtla  statuette,  228 
Tyuyoni,  ruins,  83 

United  Fruit  Co.,  216  f. 

Upper  Carbonic: 

Coal-making  in,  286 
Mountain-making  in,  278 
Upper  Cretacic,  coal-making  in,  286 
United  States  Forest  Service,  3 
Urals,  rise  of,  278,  287 
Utah,  comparison  with  Arizona,  21 
Uxmal,  ruins  of,  229 

Valladolid,  rainfall  of,  178 
Variations  in  rate  of  tree  growth,  123  ff. 

Vegetation,  causes  of  variation  in  rate  of  growth,  157 
in  relation  to  old  Otero  Lake  strands,  39  f. 
Yucatan,  178  f. 

of  Guatemala,  relation  to  climatic  changes, 
212 

monsoon  desert,  21  f. 
mountains  of  Arizona,  18 
Rio  Grande  Valley,  83 
rapidity  of  growth  in  Tropics,  181 
relation  to  terraces,  31  ff. 

Velasco,  Luis  de,  97 

Verde  River,  terraces  and  ancient  irrigation,  44 
Vallej^,  102 

Volcanic  activity,  relation  to  geological  climate,  261 

dust  in  atmosphere,  effect  on  temperature,  250  ft’ 
as  climatic  factor,  274,  286,  287 
phenomena  in  Guatemala,  211-212 
Volcanism,  and  critical  periods,  287 

mountain-making,  286 
Devonic,  287 
Eocene,  283,  287 
Liassic,  280 
Siluric,  287 

Volcanoes,  effect  on  climate,  250  ff. 

relation  to  lakes  in  Guatemala,  211 

Wakefield,  W.  J.,  57 

Walls  for  defense,  at  Charco  Yuma  (see  also  Forts),  56 
Ward,  L.  F.,  cited,  91 
Ward  Line  of  steamers,  176 

Warping  of  earth’s  crust  in  relation  to  terraces,  28  ff. 
Wars,  relation  to  changes  of  climate,  88 
Water  Canyon,  72 

Water  for  drinking  (see  Drinking  water). 

Water-supply  (see  Drinking  water;  Agriculture;  Floods; 

Drought),  of  Yucatan,  184 
Wealden  formation,  282 
Weapons  of  Hohokam,  68 
“Weather  cycles  in  the  growth  of  big  trees,”  101 


Weatherell,  Mrs.,  cited,  81 
Wells,  depth  of,  at  Nelson’s  Ranch,  57 
effect  upon  Indians,  51 
in  Yucatan,  177,  184 

Wheat  prices  in  England  compared  with  Sun-spots,  239  f. 
Whipple  Barracks,  Ariz.,  103 
White  fir,  habitat  of,  141 

oaks,  conditions  favorable  to  growth,  134 
corrective  factors  of,  132 
curve  of  growth,  133 
distribution  of,  134 
sands  of  Otero  Basin,  40  ff. 

Wild  animals,  relation  to  Hohokam,  79 
Willis,  B.,  cited,  23 

Willis  and  Blackwelder,  on  tillites  of  China,  269,  271,  272, 
293,  294 

Windmills  in  Yucatan,  177 
Winds,  effect  on  civilization,  219 
Wolf,  cited,  238 

Women,  occupations  among  Hohokam,  69 
Wood,  use  of  among  Hohokam,  77 

with  rings.  Upper  Cretacic,  282 
Wright,  J.  B.,  cited,  58 

Xochimilco  Lake,  95 

Yaxchilan  ruins,  229 

Yellow  fever,  220 

Yellow  pine,  101  ff.  (See  Pines.) 

Corrective  factors  of,  129  ff. 

Curve  of  growth,  133 
In  New  Mexico,  128 

Of  New  Mexico,  distribution  of,  128,  134 
Opposed  phases  of  growth  in  Idaho  and  New  Mexico, 
136 

Yellowstone  River,  terraces  of,  26 
Yucatan: 

Causes  of  present  depopulation,  189  f. 

Changes  of  climate  in,  189  ff. 

Civilization  of,  182  ff. 

Climate  of,  177  f. 

Coasts  of,  176 

Distribution  of  population  in,  180 
Drainage  of,  177 

Effect  of  climatic  changes  upon  seasonal  precipitation, 
206  ff. 

cool  weather  in,  210 
Former  storminess  of,  206 
Inhabitants  of,  179  ff. 

Isolation  of,  176 
Peninsula  of,  175  ff. 

Present  civilization  of,  182 

vs.  past  population,  183 
Rainfall  of,  177 

Relation  of  precipitation  to  “northers,”  206 
Topography  of,  176  f. 

Water-supply  of,  177,  184 
Vegetation  of,  178  f. 

Yuma,  climate  of,  9,  10 
rainfall,  21 

Zacapa,  terraces  at,  213 

vegetation  of,  217 
Zapote  tree,  use  for  beams,  183 
gum,  186 

Zon,  R.,  cited,  132 
Zuni  Indians,  75 

Relation  to  Hohokam,  48 
Mountains,  76 
National  Forest,  128 


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